- A stupid or silly person; a dolt.
- A person whose mental acumen is well below par.
- A person of moderate to severe mental retardation 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.
- Stupid; silly.
- Well below par in mental acumen.
[From obsolete French imbécille, weak, feeble, from Old French, from Latin imbēcillus : in-, not; see in-1 + possibly bacillum, staff, diminutive of baculum, rod.]
imbecilely im'be·cile·ly adv.




