blackboard

noun

1. A large flat surface, finished with black slate or a similar material, that can be written upon with chalk and subsequently erased; a chalkboard.

   “Drawings and pictures are more than mere ornaments in scientific discourse. Blackboard sketches, geological maps, diagrams of molecular structure, astronomical photographs, MRI images, the many varieties of statistical charts and graphs: These pictorial devices are indispensable tools for presenting evidence, for explaining a theory, for telling a story.”

verb

1. To use a blackboard to assist in an informal discussion.