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

• 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

Suppose Beijing established a lead over American AI labs and reached the cusp of recursively-improving superintelligence before us. —Dan Hendrycks, TIME, 6 Mar. 2025

Danielle Scott, a legally blind Afro-Cuban, Polish-Jewish, and Asian mixed-media artist at the cusp of international fame, risks her own well-being by exposing herself to the intergenerational trauma of the Atlantic Slave Trade. —Matthew Carey, Deadline, 7 May 2025

That journey, which has already seen the top pick of the 2021 draft endure a major injury and historic losing, earn an All-Star bid and lift the Detroit Pistons back to the playoffs, led him to the cusp of his defining moment. —Hunter Patterson, New York Times, 28 Apr. 2025

Along with fellow senior transfers Sedona Prince and Madison Conner, Van Lith helped take a TCU program that had never won more than 25 games in a season to 33 wins and the cusp of the Final Four. —Everett Cook, Axios, 28 Mar. 2025

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