Definition of "imbecile"

imbecile

/ɪmbəˈsiːl/

noun
plural imbeciles
1. (obsolete) 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.
  Quotations
  It is an offence for a man to have unlawful sexual intercourse with a woman whom he knows to be an idiot or imbecile.
  1956, Parliament of the United Kingdom, “Part I, section 7”, in Sexual Offences Act 1956‎, page 2
2. (derogatory) A fool, an idiot.
adjective
comparative more imbecile, superlative most imbecile
1. (dated) Destitute of strength, whether of body or mind; feeble; impotent; especially, mentally weak.
  Quotations
  And then that imbecile crowd down on the deck started their little fun, and I could see nothing more for smoke.
  1899 April, Joseph Conrad, “The Heart of Darkness”, in Blackwood’s Edinburgh Magazine, volume CLXV, number MII, New York, N.Y.: The Leonard Scott Publishing Company, […], part III (Conclusion), page 647