imbecile -
Destitute of strength, whether of body or mind; feeble; impotent; especially, mentally weak.
Wikipedia
Imbecile is a term for moderate to severe mental retardation, as well as for a type of criminal. It arises from the Latin word imbecillus, meaning weak, or weak-minded. "Imbecile" was once applied to people with an IQ of 26-50, between "moron" (IQ of 51-70) and "idiot" (IQ of 0-25).
OmegaWiki Dictionary
Ω
imbecile A person, especially a large male, who is clumsy or a simpleton; an idiot.