defense mechanism

noun

1

: an often unconscious mental process (such as repression) that makes possible compromise solutions to personal problems

2

: a defensive reaction by an organism

Examples of defense mechanism in a Sentence

She is projecting her anger on you as a defense mechanism.

the cell's normal defense mechanisms against infection

Recent Examples on the Web

The hardy parasite is also highly attuned to threats and responds with formidable defense mechanisms — prolonging a treatment process that’s already months to years long and often fraught with other hurdles and pain. —Kristen Rogers, CNN Money, 10 Jan. 2026

In Foster’s time away from the limelight, Hollywood missed her particular actorly touch with flintiness or with a hard edge — showing the delicacy that lies under a defense mechanism. —Daniel D'addario, Variety, 7 Jan. 2026

Part of the issue involved the grapevines’ own defense mechanism. —Nicola Twilley, New Yorker, 5 Jan. 2026

The human body had to strengthen its defense mechanisms and energy output, as per Archaeology Mag. —Maria Mocerino, Interesting Engineering, 21 Dec. 2025

Word History

First Known Use

1909, in the meaning defined at sense 1

Rhymes for defense mechanism

• abolitionism
• aldosteronism
• americanism
• anticommunism
• antisemitism
• antiterrorism
• bioterrorism
• colloquialism
• colonialism
• consequentialism
• contextualism
• conventionalism

Medical Definition

defense mechanism

noun

1

: an often unconscious mental process (as repression, projection, or sublimation) that makes possible compromise solutions to personal problems

2

: a defensive reaction by an organism