fault line

American  

noun

Geology.

• fault lines
  plural

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

---

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

---

Other Word Forms

Noun Inflected Forms

• fault lines
  plural

Etymology

Origin of fault line

First recorded in 1865–70

Example Sentences

See Examples For:

fault line

The fault line is one of Southern California’s top seismic danger zones because it runs under dense and crowded areas.

From Los Angeles Times ● Sep. 6, 2026

Some risks can be largely sidestepped: choosing not to build on an earthquake fault line, for example, or in flood plains.

From The Wall Street Journal ● Sep. 5, 2026

The row that followed exposed the real fault line that's coming to the surface this summer: not whether to cut carbon or adapt to the heat – but how much to spend on each.

From BBC ● Jul. 29, 2026

Playing a childless, 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

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