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

The episode exposed a fault line in Silicon Valley between engineers who viewed autonomous targeting as an ethical red line and defense officials who saw it as essential.

From Barron's • Apr. 5, 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

You don’t know that when a memo arrives to confirm the assignment, some deep and unseen fault line in your life has begun to tremble, that some hold is already starting to slip.

From "Becoming" by Michelle Obama

Related Words

• rift