chalk talk

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A lecture, often informal, illustrated with diagrams chalked on a blackboard.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun academia An informal lecture on an academic subject.
• noun A music hall act in which a performer makes chalk caricatures whilst reciting a monologue

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a talk that uses a blackboard and chalk