Definition of "chalk" []

• A soft compact calcite, CaCO3, with varying amounts of silica, quartz, feldspar, or other mineral impurities, generally gray-white or yellow-white and derived chiefly from fossil seashells. (noun)
• A piece of chalk or chalklike substance in crayon form, used for marking on a blackboard or other surface. (noun)
• Games A small cube of chalk used in rubbing the tip of a billiard or pool cue to increase its friction with the cue ball. (noun)
• A mark made with chalk. (noun)
• Chiefly British A score or tally. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "The phrase chalk and cheese springs to mind, or as the French say jour et nuit – day and night."
• "And in what we call our chalk talk segment, when should police officers make an arrest and when should they simply walk away?"
• "Most of my classes would be considered somewhat lecture-based, or what we call 'chalk and talk' - a fairly effective way to teach and one that I think I'm pretty good at."