fault line

American  

noun

Geology.

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

---

Etymology

Origin of fault line

First recorded in 1865–70

Example Sentences

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

From BBC • Mar. 4, 2026

The fault line exposed now is that private credit is being offered to retail investors and wealthy individuals whose liquidity preferences are different from sophisticated, more patient institutional investors.

From MarketWatch • Feb. 26, 2026

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

From The Wall Street Journal • Feb. 8, 2026

"This is significant because it means the ground shaking near the fault line might be more intense than our current hazard models predict for these types of faults."

From Science Daily • Dec. 16, 2025

The massacres had happened over two hundred years ago, but the wound they’d made in our cultural history was left raw and festering, like a fault line that may begin trembling again at any moment.

From "The City Beautiful" by Aden Polydoros

Related Words

• rift