brained (br?nd)adj. Having a brain. Often used in combination: small-brained reptiles.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.brained (bre?nd) adj. having a particular type of brain (used in combination): small-brained dinosaurs. [1400?50] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.