At the drop of a hat

a small quantity of liquid that falls or is produced in a more or less spherical mass; a liquid globule.
the quantity of liquid contained in such a globule.
a very small quantity of liquid:
I’ll have a little more tea, just a drop.
a minute quantity of anything:
not even a drop of mercy.
Usually, drops.

liquid medicine given in a dose or form of globules from a medicine .
a solution for dilating the pupils of the eyes, administered to the eyes in globules by a medicine dropper.

a limited amount of an alcoholic beverage:
He occasionally takes a drop after dinner.
an act or instance of dropping; fall; descent.
the distance or depth to which anything drops:
a ten-foot drop to the ground.
a steep slope:
a short drop to the lake.
a decline in amount, degree, quality, value, etc.:
a drop in prices.
a small, usually spherical, piece of candy; lozenge:
a lemon drop.
a central depository where items are left or transmitted:
a mail drop.
a predesignated place where secret letters or packages can be left to be picked up by another person without attracting attention, as in espionage or drug dealing.
something resembling or likened to a liquid globule, as certain ornaments, a spherical earring, etc.
a pendant.
a descent by parachute.
an instance of dropping supplies by parachute or an amount of supplies so dropped.
something that drops or is used for dropping.
a group of persons dropped by parachute, as the personnel dropped by parachute during one military action.
Theater.

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.

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a gallows.
a slit or opening into which something can be dropped, as in a mailbox.
(in a casino) the income from the sale of chips.
a small flag, usually of enameled metal, that gives a visual signal in an annunciator.
Furniture. an applied ornament resembling a pendant.
Architecture, (def 2).
Nautical. the vertical dimension amidships of any sail that is bent to a standing yard.
Compare (def 6a).
Also called drop panel. (in reinforced-concrete-slab construction) a thickened portion of the ceiling around a column head.
Horology. the free motion of an escape wheel between successive checks by the pallet.
the newborn young of an animal.
to fall in globules or small portions, as water or other liquid:
Rain drops from the clouds.
to fall vertically; have an abrupt descent.
to sink or fall to the ground, floor, or bottom as if inanimate.
to fall lower in condition, degree, value, etc.; diminish or lessen; sink:
The prices dropped sharply.
to come to an end; cease; lapse:
There the matter dropped.
to fall or move to a position that is lower, farther back, inferior, etc.:
to drop back in line; to drop to the rear.
to withdraw; quit (often followed by out or from):
to drop out of a race; to drop from a game.
to pass or enter without effort into some condition, activity, or the like:
to drop into sleep; to drop into a habit.
to make an unexpected or unannounced stop at a place; pay an informal visit or call (usually followed by in, by, or over):
Since we’re in the neighborhood, why don’t we drop in at my brother’s?
to cease to appear or be seen; vanish:
to drop from sight or notice.
to fall wounded, dead, etc.:
A thousand men dropped in the battle.
to squat or crouch, as a dog at the sight of game.
to move gently, as with the tide or a light wind (usually followed by down).
Slang. to ingest an illicit drug orally; swallow.
to let fall in drops or small portions:
to drop lemon juice into tea.
to let or cause to fall.
to cause or allow to sink to a lower position.
to cause to decrease in value, amount, quality, etc.; reduce.
to utter or express casually or incidentally:
to drop a hint.
to write and send:
Drop me a note.
to bring to the ground by a blow or shot.
to set down or unload, as from a ship, car, etc. (often followed by off):
Drop me at the corner.
to omit (a letter or syllable) in pronunciation or writing:
He dropped his h’s.
to lower (the voice) in pitch or loudness.
to cease to keep up or have to do with:
I dropped the subject. Will you drop your old friends if you win the lottery?
to cease to employ, admit as a member, or include, as on a list; dismiss:
to drop an accountant from the payroll; to drop three members of the club who have not paid their dues.
to withdraw or cease to pursue:
The police dropped the charges against the suspect.
Sports.

to throw, shoot, hit, kick, or roll (a ball, puck, etc.) through or into a basket, hole, or other goal:
He dropped the ball through the basket for two points.
to lose (a game or contest):
They dropped two games in a row and were eliminated from the tournament.

Football.

to drop-kick (a ball).
to score with a .

(of animals) to give birth to:
The cat dropped a litter of six kittens.
to parachute (persons, supplies, etc.):
The Marines dropped 300 combat troops into the jungle battlefield.
to lengthen by lowering or letting out:
to drop the hem of a skirt.
to lower (the wheels) into position for landing an airplane.
Slang. to take (especially an illicit drug) by swallowing; ingest:
to drop LSD.
Nautical. to pass out of sight of; outdistance.
Cookery. to poach (an egg).
drop behind, to fall short of the required pace or progress:
Her long illness caused her to drop behind the rest of the class.
drop off,

to fall asleep.
to decrease; decline:
Sales have dropped off drastically.

drop out,

to withdraw from being a member or participant:
to drop out of a club; to drop out of society and become a wanderer.
to stop attending school or college.

at the drop of a hat, at the slightest provocation or without delay:
He’s ready to fight at the drop of a hat.
drop dead, (used as an expression of contempt, disgust, impatience, etc.):
If that’s the way you feel about it, drop dead!
drop in the bucket. (def 13).
get / have the drop on,

to aim and be ready to shoot a gun at an antagonist before the other person’s gun can be drawn.
to get or have at a disadvantage.

noun
a small quantity of liquid that forms or falls in a spherical or pear-shaped mass; globule
a very small quantity of liquid
a very small quantity of anything
something resembling a drop in shape or size, such as a decorative pendant or small sweet
the act or an instance of falling; descent
a decrease in amount or value; slump: a drop in prices
the vertical distance that anything may fall
a steep or sheer incline or slope
short for fruit drop
the act of unloading troops, equipment, or supplies by parachute
(in cable television) a short spur from a trunk cable that feeds signals to an individual house
(theatre) See drop curtain
another word for trap door, gallows
(mainly US & Canadian) a slot or aperture through which an object can be dropped to fall into a receptacle
(nautical) the midships height of a sail bent to a fixed yard Compare hoist (sense 6a)
(Austral, cricket, slang) a fall of the wicket: he came in at first drop
See drop shot
a drop in the bucket, a drop in the ocean, an amount very small in relation to what is needed or desired
at the drop of a hat, without hesitation or delay
have had a drop too much, to be drunk
(US & NZ) have the drop on someone, to have the advantage over someone
verb drops, dropping, dropped
(of liquids) to fall or allow to fall in globules
to fall or allow to fall vertically
(transitive) to allow to fall by letting go of
to sink or fall or cause to sink or fall to the ground, as from a blow, wound, shot, weariness, etc
(intransitive; foll by back, behind, etc) to fall, move, or go in a specified manner, direction, etc
(intransitive; foll by in, by, etc) (informal) to pay a casual visit (to)
to decrease or cause to decrease in amount or value: the cost of living never drops
to sink or cause to sink to a lower position, as on a scale
to make or become less in strength, volume, etc
(intransitive) to sink or decline in health or condition
(intransitive) sometimes foll by into. to pass easily into a state or condition: to drop into a habit
(intransitive) to move along gently as with a current of water or air
(transitive) to allow to pass casually in conversation: to drop a hint
(transitive) to leave out (a word or letter)
(transitive) to set down or unload (passengers or goods)
(transitive) to send or post: drop me a line/text/email
(transitive) to discontinue; terminate: let’s drop the matter
(transitive) to cease to associate or have to do with
(transitive) (slang, mainly US) to cease to employ: he was dropped from his job
(transitive; sometimes foll by in, off, etc) (informal) to leave or deposit, esp at a specified place
(of animals) to give birth to (offspring)
(slang, mainly US & Canadian) to lose (money), esp when gambling
(transitive) to lengthen (a hem, etc)
(transitive) to unload (troops, equipment, or supplies) by parachute
(transitive) (nautical) to leave behind; sail out of sight of
(transitive) (sport) to omit (a player) from a team
(transitive) to lose (a score, game, or contest): the champion dropped his first service game
(transitive) (sport) to hit or throw (a ball) into a goal: he dropped a 30 foot putt
(transitive) to hit (a ball) with a drop shot
(nautical) drop astern, to fall back to the stern (of another vessel)
(transitive) (motor racing, slang) to spin (the car) and (usually) crash out of the race
(transitive) (slang) to swallow (a drug, esp a barbiturate or LSD)
(slang) drop dead!, an exclamation of contempt
noun, verb
(rugby) short for drop kick or drop-kick
n.

Old English dropa “a drop of liquid,” from Proto-Germanic *drupon (cf. Old Saxon dropo, Old Norse dropi, Dutch drop, Old High German tropfo, German Tropfen (n.)), from PIE *dhreu-.

Meaning “an act of dropping” is from 1630s; of immaterial things (prices, temperatures, etc.) from mid-19c. Meaning “lozenge, hard candy” is 1723. Meaning “secret place where things can be left illicitly and picked up later” is from 1931.

Drop in the bucket (late 14c.) is from Isa. ix:15 [KJV]. At the drop of a hat “suddenly” is from 1854; drop-in “casual visit” is 1819; drop-kick is 1857. To get the drop on someone originally was Old West gunslinger slang (1869).
v.

Old English dropian “to fall in drops” (see drop (n.)). Meaning “to fall vertically” is late 14c. Transitive sense “allow to fall” is mid-14c. Related: Dropped; dropping. Exclamation drop dead is from 1934; as an adjective meaning “stunning, excellent” it is first recorded 1970.

drop (drŏp)
n.

The smallest quantity of liquid heavy enough to fall in a spherical mass.

A volume of liquid equal to 1/76 of a teaspoon and regarded as a unit of dosage for medication.

A small globular piece of candy, usually readily dissolved in the mouth.

v. dropped, drop·ping, drops
To fall, be dispensed, or poured in drops.

noun

(also drop joint) A seemingly honest place used as a cover for illegal matters, esp as a depot for stolen goods; fence (1930s+ Underworld)
mail drop (1950s+)
A drink or drinks: I could see by his careful walking he’d taken a drop (1775+)
A homeless slum boy: accepting anywhere from 25 cents to $1 a week for taking in drops, rustles, fetches (1950s+ Black)
A paying passenger (1950s+ Cabdrivers)
The base fee on a taxi meter registered when the cabdriver activates the meter (1950s+ Cabdrivers)

verb

To be arrested; be caught with loot; fall (1900+ Underworld)
To knock someone down; deck (1812+)
To kill someone, esp by shooting; bump, off, whack (1726+)
To lose, esp money: He dropped a bundle in the market yesterday (1676+)
To collapse, esp with fatigue: I’ll drop if I don’t sit down (1400+)
To stop seeing or associating with someone: She dropped her boyfriend (1605+)
To take any narcotic, esp in pill or capsule form: We want a society where you can smoke grass and drop acid (1960s+ Narcotics)

Related Terms

get the drop on someone, knockout drops
Immediately, without delay, as in We were ready to pack our bags and go on vacation at the drop of a hat. This phrase probably alludes to signaling the start of a race or other contest by dropping a hat. [ Late 1800s ]

drop a bombshell
drop a brick
drop a dime
drop a line
drop back
drop behind
drop by
drop dead
drop in one’s tracks
drop in someone’s lap
drop in the bucket
drop like a hot potato
drop like flies
drop names
drop off
drop out
drop the ball

also see:

at the drop of a hat
bottom drops out of
get the drop on
hear a pin drop
let drop
wait for the other shoe to drop