IDIOCY
idiocy, amentia
(noun) extreme mental retardation
Source: WordNet® 3.1
Etymology
Noun
idiocy (countable and uncountable, plural idiocies)
(psychology) The state or condition of being an idiot; the quality of having an intelligence level far below average; mental retardation.
An act lacking intelligence or sense; an instance of senselessness; extremely foolish behaviour.
Synonyms
• imbecility
• stupidity
Anagrams
• dioicy
Source: Wiktionary
Id"i*o*cy, n. Etym: [From idiot; cf. Gr. Idiot, and cf. Idiotcy.]
Definition: The condition or quality of being an idiot; absence, or marked
deficiency, of sense and intelligence.
I will undertake to convict a man of idiocy, if he can not see the
proof that three angles of a triangle are equal to two right angles.
F. W. Robertson.
Source: Webster’s Unabridged Dictionary 1913 Edition