What is the meaning of Imbecile?

A person with limited mental capacity who can perform tasks and think only like a young child, in medical circles meaning a person who lacks the capacity to develop beyond the mental age of a normal five- to seven-year-old child.

A fool, an idiot.

Destitute of strength, whether of body or mind; feeble; impotent; especially, mentally weak.

↑ Walker, John (1791), “Imbecile”, in A Critical Pronouncing Dictionary […] , London: G. G. J. and J. Robinſon […] and T. Cadell, →OCLC, page 289, column 3 of 3.

Source: wiktionary.org