Bob–up

a short, jerky motion:
a bob of the head.
to move quickly down and up:
to bob the head.
to indicate with such a motion:
to bob a greeting.
to make a jerky motion with the head or body.
to move about with jerky, usually rising and falling motions:
The ball bobbed upon the waves.
bob up, to emerge or appear, especially unexpectedly:
A familiar face bobbed up in the crowd.
Historical Examples

Encyclopaedia Britannica, 11th Edition, Volume 5, Slice 2 Various
The Tale of Benny Badger Arthur Scott Bailey
Latitude 19 degree Mrs. Schuyler Crowninshield
The New Girl at St. Chad’s Angela Brazil
The Awful Australian Valerie Desmond
Mari, Our Little Norwegian Cousin Mary Hazelton Wade
Representative Plays by American Dramatists: 1856-1911: The New York Idea Langdon Mitchell
For the Honor of Randall Lester Chadwick
Tropic Days E. J. Banfield
The Shadow Arthur Stringer

verb bobs, bobbing, bobbed
to move or cause to move up and down repeatedly, as while floating in water
to move or cause to move with a short abrupt movement, as of the head
to make (a bow or curtsy): the little girl bobbed before the visitor
(intransitive) usually foll by up. to appear or emerge suddenly
(intransitive; foll by under, below, etc) to disappear suddenly, as beneath a surface
(intransitive) usually foll by for. to attempt to get hold (of a floating or hanging object, esp an apple) in the teeth as a game
noun
a short abrupt movement, as of the head
a quick curtsy or bow
(bell-ringing) a particular set of changes
(angling)

short for bobfloat
the topmost fly on a cast of three, often fished bobbing at the surface
this position on a wet-fly cast

noun
a hairstyle for women and children in which the hair is cut short evenly all round the head
a dangling or hanging object, such as the weight on a pendulum or on a plumb line
a polishing disc on a rotating spindle. It is usually made of felt, leather, etc, impregnated with an abrasive material
short for bob skate, bobsleigh
a runner or pair of runners on a bobsled
(angling) a small knot of worms, maggots, etc, used as bait
a very short line of verse at the end of a stanza or preceding a rhyming quatrain (the wheel) at the end of a stanza
a refrain or burden with such a short line or lines
a docked tail, esp of a horse
(Brit, dialect) a hanging cluster, as of flowers or ribbons
verb bobs, bobbing, bobbed
(transitive) to cut (the hair) in a bob
(transitive) to cut short (something, esp the tail of an animal); dock or crop
(intransitive) to ride on a bobsled
verb bobs, bobbing, bobbed
to tap or cause to tap or knock lightly (against)
noun
a light knock; tap
noun (pl) bob
(Brit) (formerly) an informal word for a shilling (sense 1)
noun
(slang) Bob’s your uncle, everything is or will turn out all right
v.
n.
best of breed
Bolivia-boliviano
Bureau of the Budget
Appear suddenly or unexpectedly. For example, I didn’t know anyone in the group until Harry bobbed up. This term uses the verb bob in the sense of “to bounce,” a usage dating from Chaucer’s day. [ Late 1800s ]