noun.
A smooth, hard, dark-colored panel for writing on with chalk.
The Century Dictionary and Cyclopedia
noun.
A board painted black, used in schools, lecture-rooms, etc., for writing, drawing, or ciphering with chalk.
noun.
Hence Any prepared surface, as of plaster or slate, used for the same purpose.
the GNU version of the Collaborative International Dictionary of English
noun.
A broad board painted black, or any black surface on which writing, drawing, or the working of mathematical problems can be done with chalk or crayons. It is much used in schools. In late 20th century similar boards of a green slate as well as some colored white became common; wrioting on the slate bioards may be done with chalk, but writing on the white boards is done with colored pens, such as grease pens, which leaves a trace that can be easily erased. The newer boards, usualy called chalkboards are nevertheless still sometimes referred to as blackboards.
noun.
A large flat surface, finished with black slate or a similar material, that can be written upon with chalk and subsequently erased; a chalkboard
verb.
To use a blackboard to assist in an informal discussion.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
noun.
sheet of slate; for writing with chalk
Word Usage
"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!)."