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

However, anyone watching an eclipsed sun on the cusp of setting while on a beach in the Balearic Islands in 2026 will have just as much drama — if not more. —Jamie Carter, Space.com, 10 May 2026

Years later, fashion designer Tommy Hilfiger bought those boots, which are now on the cusp of a reboot. —Lisa Gutierrez may 8, Kansas City Star, 8 May 2026

With Vuckovich on the cusp of his 90th birthday, the seven-decade spread between the pianist and Tang embodies jazz’s crucial generational reach, with young players imbibing essential seasoning via direct contact with veteran masters. —Andrew Gilbert, Mercury News, 7 May 2026

Yulieth, on the cusp of adolescence, faces the difficulties of growing up in a wild territory where natural beauty coexists with the hostility of machismo. —Matthew Carey, Deadline, 6 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