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

Wall Street may be on the cusp of one of the most consequential initial public offering (IPO) waves in years. —Marc Cooper, Forbes.com, 28 May 2026

Hello Sanctos entered the Spruce Meadows ‘Masters’ in 2015 on the cusp of history. —Danielle Rossingh, New York Times, 27 May 2026

From a new wave of design-forward hotels, to no-frills seaside villages, wild nature, scenic islands and an art and culture scene that is having a moment, the Var is on the cusp of a moment of its own. —Monica Mendal, Vogue, 25 May 2026

Stock market bulls wrestled back control last week after a brief respite, putting the S & P 500 back on the cusp of another record high. —Morgan Chittum, CNBC, 23 May 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