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.
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