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
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Clean energy, on the other hand, has served as a critical defense mechanism that has kept the energy price crisis from getting worse in places where it has been deployed at scale. — Justin Worland, Time, 17 Oct. 2026 Several years ago, a tree expert of some sort told me the main reason oaks didn’t produce acorns every year is because of a natural defense mechanism. — Colin Moore, Outdoor Life, 2 Sep. 2026 On Podium, Cheekface dial up both the hooks and the sociopolitical dread, but absurdist humor remains their defense mechanism for a world spiraling out of control. — Zach Schonfeld, Pitchfork, 3 Aug. 2026 This ritual acts as a defense mechanism, creating visible motion to absorb pressure while the fundamental structure remains unchanged. — Vibhas Ratanjee, Forbes.com, 31 July 2026 See All Example Sentences for defense mechanism

Word History

First Known Use

1909, in the meaning defined at sense 1

Time Traveler
The first known use of defense mechanism was in 1909

Rhymes for defense mechanism

See All Rhymes for defense mechanism

Browse Nearby Words

defenseman
defense mechanism
defensibility
See all Nearby Words

Cite this Entry

“Defense mechanism.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/defense%20mechanism. Accessed 22 Oct. 2026.

Copy Citation

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

More from Merriam-Webster on defense mechanism

Britannica.com: Encyclopedia article about defense mechanism

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

Last Updated: - Updated example sentences

More from Merriam-Webster

Word of the Day

Listen to the pronunciation of vocation

See Definitions and Examples »

Popular in Grammar & Usage

See More

Merriam-Webster’s Great Big List of Words You Love to Hate

'Can' vs. 'May'

'Affect' vs. 'Effect'

More Commonly Mispronounced Words

Is it 'nerve-racking' or 'nerve-wracking'?
See More

Popular in Wordplay

See More

The Longest Long Words List

9 Words That Sound Like Insults But Aren't

Did 'orange' the fruit or the color come first?

Even More Bird Names that Sound Like Insults (and Sometimes Are)

12 Lovely and Unusual Words for the Natural World
See More

Popular

See More

Merriam-Webster’s Great Big List of Words You Love to Hate

The Longest Long Words List

9 Words That Sound Like Insults But Aren't
See More

Games & Quizzes

See All
Play Quordle: Guess all four words in a limited number of tries. Each of your guesses must be a real 5-letter word.
Quordle Can you solve 4 words at once?
Play Blossom: Solve today's spelling word game by finding as many words as you can using just 7 letters. Longer words score more points.
Blossom Pick the best words!
Play Missing Letter: a crossword with a twist. Each of the 25 puzzle words start with a different letter of the alphabet. Which letter is missing?
The Missing Letter A daily crossword with a twist
artwork of illustrated limes with the text limes and smile with an arrow connecting the two words
Quiz: Spot the Anagram! Scramble these words to find new words with the e...
See All