Definition of "blackboard" []

• A smooth, hard, dark-colored panel for writing on with chalk. (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 monster crystals, over six meters long, are made of selenite, a crystalline form of the mineral gypsum (the number one ingredient in blackboard chalk!)."
• "I don’t draw in blackboard chalks like these others, I use proper colours the same as what painters use; bloody expensive they are, especially the reds."
• "Each blackboard is provided with a small case in which are kept the chalk, and the white cloths which we use instead of the ordinary erasers."