Definition of "Chalk" :

noun: a piece of calcite or a similar substance, usually in the shape of a crayon, that is used to write or draw on blackboards or other flat surfaces

noun: an amphetamine derivative (trade name Methedrine) used in the form of a crystalline hydrochloride; used as a stimulant to the nervous system and as an appetite suppressant

noun: a pure flat white with little reflectance

noun: a soft whitish calcite

verb: write, draw, or trace with chalk