from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun A person who is considered foolish or stupid.
  • noun A person of moderate to severe mental retardation having a mental age of from three to seven years and generally being capable of some degree of communication and performance of simple tasks under supervision. The term belongs to a classification system no longer in use and is now considered offensive.

from The Century Dictionary.

  • To make imbecile; weaken.
  • To embezzle.
  • Without physical strength; feeble; impotent; helpless.
  • Mentally feeble: fatuous; having the mental faculties undeveloped or greatly impaired. See imbecility.
  • Marked by mental feebleness or incapacity; indicating weakness of mind; inane; stupid: as, imbecile efforts; an imbecile speech.
  • Synonyms and Foolish, driveling, idiotic. See debility.
  • noun One who is imbecile.

from the GNU version of the Collaborative International Dictionary of English.

  • adjective Destitute of strength, whether of body or mind; feeble; impotent; esp., mentally wea; feeble-minded.
  • noun One destitute of strength; esp., one of feeble mind; -- sometimes used as a pejorative term.
  • noun (Psychology) A person with a degree of mental retardation between that of an idiot and a moron; in a former classification of mentally retarded person, it applied to a person with an adult mental age of from four to eith years, and an I.Q. of from 26 to 50.
  • transitive verb obsolete To weaken; to make imbecile.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun 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.
  • noun pejorative A fool, an idiot.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • noun a person of subnormal intelligence
  • adjective having a mental age of three to seven years


from The American Heritage® Dictionary of the English Language, 4th Edition

[From obsolete French imbécille, weak, feeble, from Old French, from Latin imbēcillus : in-, not; see in– + possibly bacillum, staff, diminutive of baculum, rod; see bak- in Indo-European roots.]

from Wiktionary, Creative Commons Attribution/Share-Alike License

From Latin imbēcillus ("weak, feeble"), literally “without a staff”.


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  • By the way go easy with that money like a good young imbecile. Yes, I must.

    Joyce, Ulysses, 3

    December 30, 2006

  • Citation as adjective at sedge.

    November 13, 2008

  • And apparently there's a number: having an IQ of between 25 and 50.

    (So worse than a moron.)

    July 1, 2009