bed head or bed·head (b?d?h?d?)n. Slang Hair that is unkempt, matted, or tousled, especially from being compressed or disheveled during sleep.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.