[im-buh-sil, -suh l or, esp. British, -seel]


Informal. a dunce; blockhead; dolt: Don't stand there like an imbecile. Open the door!.
Psychology. (no longer in technical use; now considered offensive) a person of the second order in a former and discarded classification of mental retardation, above the level of idiocy, having a mental age of seven or eight years and an intelligence quotient of 25 to 50.


Informal. stupid; silly; absurd.
Usually Offensive. showing mental feebleness or incapacity.
Archaic. weak or feeble.

Origin of imbecile

1540–50; earlier imbecill < Latin imbēcillus weak; -ile replacing -ill by confusion with suffix -ile
Related formsim·be·cil·ic, adjectiveim·be·cile·ly, adverb Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for imbecile

Historical Examples of imbecile

  • I do not know whose heads are criminal, but I think I know whose are imbecile.

    Alarms and Discursions

    G. K. Chesterton

  • The imbecile baron then got out; his shoulder was out of joint.

    My Double Life

    Sarah Bernhardt

  • A man, aged 22, the son of an inebriate, with one imbecile sister.

  • He spent a whole evening measuring this imbecile's facial angle.

  • He flew into a passion, disowned his discovery, and called himself an imbecile.

    Doctor Pascal

    Emile Zola

British Dictionary definitions for imbecile


noun (ˈɪmbɪˌsiːl, -ˌsaɪl)

psychol a person of very low intelligence (IQ of 25 to 50), usually capable only of guarding himself against danger and of performing simple mechanical tasks under supervision
informal an extremely stupid person; dolt

adjective Also: imbecilic (ˌɪmbɪˈsɪlɪk)

of or like an imbecile; mentally deficient; feeble-minded
stupid or senselessan imbecile thing to do
Derived Formsimbecilely or imbecilically, adverbimbecility, noun

Word Origin for imbecile

C16: from Latin imbēcillus feeble (physically or mentally)
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for imbecile

1540s, imbecille "weak, feeble" (especially in reference to the body), from Middle French imbecile (15c.), from Latin imbecillus "weak, feeble" (see imbecility). Sense shifted to mental weakness from mid-18c. As a noun, "feeble-minded person," it is attested from 1802. Traditionally an adult with a mental age of roughly 6 to 9 (above an idiot but beneath a moron).

Online Etymology Dictionary, © 2010 Douglas Harper

imbecile in Medicine


[ĭmbə-sĭl, -səl]


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.
Related formsimbe•cil′i•ty (-sĭlĭ•tē) n.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.