Chalk

a soft, white, powdery limestone consisting chiefly of fossil shells of foraminifers.
a prepared piece of chalk or chalklike substance for marking, as a blackboard crayon.
a mark made with chalk.
a score or tally.
to mark or write with chalk.
to rub over or whiten with chalk.
to treat or mix with chalk:
to chalk a billiard cue.
to make pale; blanch:
Terror chalked her face.
(of paint) to powder from weathering.
of, made of, or drawn with chalk.
chalk up,

to score or earn:
They chalked up two runs in the first inning.
to charge or ascribe to:
It was a poor performance, but may be chalked up to lack of practice.

noun
a soft fine-grained white sedimentary rock consisting of nearly pure calcium carbonate, containing minute fossil fragments of marine organisms, usually without a cementing material
a piece of chalk or a substance like chalk, often coloured, used for writing and drawing on a blackboard
a line, mark, etc made with chalk
(billiards, snooker) a small cube of prepared chalk or similar substance for rubbing the tip of a cue
(Brit) a score, tally, or record
(informal) as alike as chalk and cheese, as different as chalk and cheese, totally different in essentials
(Brit, informal) by a long chalk, by far
can’t tell chalk from cheese, doesn’t know chalk from cheese, to be unable to judge or appreciate important differences
(Brit, informal) not by a long chalk, by no means; not possibly
(modifier) made of chalk
verb
to draw or mark (something) with chalk
(transitive) to mark, rub, or whiten with or as if with chalk
(intransitive) (of paint) to become chalky; powder
(transitive) to spread chalk on (land) as a fertilizer
n.

Old English cealc “chalk, lime, plaster; pebble,” a West Germanic borrowing from Latin calx (2) “limestone, lime (crushed limestone), small stone,” from Greek khalix “small pebble,” which many trace to a PIE root for “split, break up.” In most Germanic languages still with the “limestone” sense, but in English transferred to the opaque, white, soft limestone found abundantly in the south of the island. Modern spelling is from early 14c. The Latin word for “chalk” was creta, which also is of unknown origin.
v.

1570s, “to mix with chalk;” 1590s as “to mark with chalk,” from chalk (n.). Related: Chalked; chalking. Old English had cealcian “to whiten.” Certain chalk marks on shipped objects meant “admitted” or “shipped free,” hence some figurative senses. Chalk boards also were commonly used in keeping credit, score, etc., hence figurative use of chalk it up (1903).
chalk
(chôk)
A soft, white, gray, or yellow limestone consisting mainly of calcium carbonate and formed primarily from the accumulation of fossil microorganisms such as foraminifera and calcareous algae. Chalk is used in making lime, cement, and fertilizers, and as a whitening pigment in ceramics, paints, and cosmetics. The chalk used in classrooms is usually artificial.

noun

A horse favored to win

[1950s+ Horse racing; References to winning by a long chalk, an allusion to scoring points by a chalk mark, date from the 1830s]