fault line

American  

noun

Geology.

1. the intersection of a fault with the surface of the earth or other plane of reference.

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fault line British  

noun

1. Also called: fault plane.  geology the surface of a fault fracture along which the rocks have been displaced

2. a potentially disruptive division or area of contention

   Europe remains the main fault line in the Tory Party

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Etymology

Origin of fault line

First recorded in 1865–70

Example Sentences

Playing a vain, pitch-perfect vision of Los Angeles’ wickedness in “Maps to the Stars,” Julianne Moore mothered so hard she almost separated California right down the San Andreas fault line.

From Salon • May 10, 2026

But Wales's decision to include glass has become a major fault line with industry representatives.

From BBC • Mar. 4, 2026

He astutely flags “medical gatekeeping” as an emerging fault line.

From The Wall Street Journal • Feb. 8, 2026

“The deeper fault line here is not trade flows. It is capital,” wrote Stephen Innes, managing partner at SPI Asset Management, in a Sunday note.

From MarketWatch • Jan. 19, 2026

But a fault line ran through the center of his thinking, a kind of mysterious region where ideas entered going in one direction but then emerged headed the opposite way.

From "Founding Brothers: The Revolutionary Generation" by Joseph J. Ellis

Related Words

• rift