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

Even well-meaning input can trigger the brain’s defense mechanisms. —Dr. Diane Hamilton, Forbes.com, 5 Apr. 2025

Bernstein says that instinct is likely a defense mechanism. —Erica Sweeney, Time, 26 Mar. 2025

Challenges of detecting resistance Antimicrobial resistance is a natural process where microbes constantly evolve as a defense mechanism, acquiring genetic changes that enhance their survival. —Nneka Vivian Iduu, The Conversation, 24 Mar. 2025

Now, scientists have discovered a surprising new technique that appears to be a defense mechanism: Some male octopuses use venom to avoid being eaten by their female mates. —Sarah Kuta, Smithsonian Magazine, 11 Mar. 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