[dih-fens or especially for 7, 9, dee-fens]
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  1. resistance against attack; protection: Two more regiments are needed for the defense of the city.
  2. something that defends, as a fortification, physical or mental quality, or medication: This fort was once the main defense of the island.
  3. the defending of a cause or the like by speech, argument, etc.: He spoke in defense of the nation's foreign policy.
  4. a speech, argument, etc., in vindication: She delivered a defense of free enterprise.
  5. Law.
    1. the denial or pleading of the defendant in answer to the claim or charge that has been made.
    2. the proceedings adopted by a defendant, or the defendant's legal agents, for defending against the charges that have been made.
    3. a defendant and his or her counsel.
  6. Psychology. defense mechanism(def 2).
  7. Sports.
    1. the practice or art of defending oneself or one's goal against attack, as in fencing, boxing, soccer, or football.
    2. the team attempting to thwart the attack of the team having the ball or puck.
    3. the players of a team who line up in their own defensive zone.
    4. the positions on the field, ice, etc., taken by such players.
  8. (initial capital letter) Also called Defense Department. Informal. the Department of Defense.
verb (used with object), de·fensed, de·fens·ing.
  1. Sports. to defend against (an opponent, play, or tactic).
Also especially British, defence.

Origin of defense

1250–1300; Middle English < Old French < Late Latin dēfēnsa a forbidding, noun use of feminine of past participle of Latin dēfendere to defend; replacing Middle English defens < Anglo-French, Old French < Medieval Latin defēnsum (thing) forbidden, neuter past participle of Latin dēfendere
Related formsde·fense·less, adjectivede·fense·less·ly, adverbde·fense·less·ness, nounnon·de·fense, noun, adjectivepre·de·fense, nounun·de·fensed, adjective

Synonyms for defense

See more synonyms for on Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

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Word Origin and History for defense

c.1300, "forbidding, prohibition," also "action of guarding or protecting," from Old French defense, from Latin defensus, past participle of defendere "ward off, protect" (see defend). But it also arrived (without the final -e) from Old French defens, from Latin defensum "thing protected or forbidden," neuter past participle of defendere.

Defens was assimilated into defense, but not before it inspired the alternative spelling defence, via the same tendency that produced hence (hennis), pence (penies), dunce (Duns). First used 1935 as a euphemism for "national military resources." Defense mechanism in psychology is from 1913.

Online Etymology Dictionary, © 2010 Douglas Harper

defense in Medicine


  1. A means or method that helps protect the body or mind, as against disease or anxiety.
Related formsde•fensive (-fĕnsĭv) adj.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.