imbecile

noun

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.

   “It is an offence for a man to have unlawful sexual intercourse with a woman whom he knows to be an idiot or imbecile.”

2. (derogatory)A fool, an idiot.

   “VLADIMIR: Because he wouldn't save them. / ESTRAGON: From hell? / VLADIMIR: Imbecile! From death.”

   ““A rat picked up a drink can and threw it at me?” yelled Mr Big. “A big rat, guv’nor? One of them super-rats?” suggested Thumbs. “It landed on my head, you imbecile!””

adj

1. (dated)Destitute of strength, whether of body or mind; feeble; impotent; especially, mentally weak.

   “hospitals for the imbecile and insane”

   “And then that imbecile crowd down on the deck started their little fun, and I could see nothing more for smoke.”