im·be·cile (ĭmbə-sĭl, -səl)
1. A person who is considered foolish or stupid.
2. A person with moderate to severe intellectual disability having a mental age of from three to seven years and generally being capable of some degree of communication and performance of simple tasks under supervision. The term belongs to a classification system no longer in use and is now considered offensive.
[From obsolete French imbécille, weak, feeble, from Old French, from Latin imbēcillus : in-, not; see IN–1 + possibly bacillum, staff, diminutive of baculum, rod; see bak- in the Appendix of Indo-European roots.]
im′be·cilic (-sĭlĭk) adv.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
The American Heritage Dictionary Blog
Check out our blog, updated regularly, for new words and revised definitions, interesting images from the 5th edition, discussions of usage, and more.