Informal A relatively great amount of knowledge: a headful of baseball trivia; a headful of good stories.
Informal An amount that covers the surface of the head, usually except for the face: a headful of auburn curls; a headful of shampoo.
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.