cusp

noun

ˈkəsp 

: point, apex: such as

a

: a point of transition (as from one historical period to the next) : turning point

also : edge, verge

on the cusp of stardom

… you're on the cusp between heat exhaustion and life-threatening heatstroke.

—Mark Jannot

b

: either horn of a crescent moon

c

: a fixed point on a mathematical curve at which a point tracing the curve would exactly reverse its direction of motion

d

: an ornamental pointed projection formed by or arising from the intersection of two arcs or foils (see foil entry 2 sense 4)

e(1)

: a point on the grinding surface of a tooth

(2)

: a fold or flap of a cardiac valve

cuspate

ˈkə-ˌspāt 

-spət

adjective

cusped

ˈkəspt 

adjective

Illustration of cusp

• 1 cusp d

Synonyms of cusp

• verge
• brink

Examples of cusp in a Sentence

the cusp of a tooth

medical researchers who are on the cusp of a major breakthrough

Recent Examples on the Web

Despite the drop, the 30-year yield is still trading on the cusp of its highest levels in 19 years. — John Towfighi, CNN Money, 19 Aug. 2026

With that, and with their walk-off in San Diego, the Padres leapt from the cusp of the wild-card picture to the thick of it. — Dennis Lin, New York Times, 13 Aug. 2026

The inability to imagine a middle-class life—especially for the Subaru Socialists right on the cusp of comfort—seems to be what’s behind a slate of recent electoral victories for the Democratic Socialists of America. — Jay Caspian Kang, New Yorker, 4 Aug. 2026

Pandemic restrictions heavily curtailed his first season, while a wave of antitrust litigation challenged the economic foundation of the NCAA and California moved to the cusp of ushering in the NIL era through state-level legislation. — Daniel Libit, Sportico.com, 23 July 2026

Word History

Etymology

Latin cuspis point

First Known Use

1585, in the meaning defined above

Phrases Containing cusp

• on the cusp

Kids Definition

cusp

noun

ˈkəsp 

: a point or pointed end or part: as

a

: either of the pointed ends of a crescent moon

b

: a point on the grinding surface of a tooth

c

: a fold or flap of a heart valve

Medical Definition

cusp

noun

ˈkəsp 

1

: a point on the grinding surface of a tooth

2

: a fold or flap of a cardiac valve

cuspal

ˈkəs-pəl 

adjective