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

Man Ray is one of the few Dada-Surrealist cusp figures who finessed affiliations with both movements without alienating either one. —Zachary Fine, New Yorker, 23 Sep. 2025

In 2023, Nvidia was at the cusp of being valued as a trillion-dollar company. —Yeo Boon Ping, CNBC, 19 Sep. 2025

While neither poses any immediate threats to Florida, one system is right on the cusp of forming into a tropical depression or storm (potentially named Gabrielle). —Alex Harris, Miami Herald, 16 Sep. 2025

Now, two years later, Viskari stands at the cusp of his junior season at Missouri as one of the Tigers’ top golfers. —Zach Sweet, Kansas City Star, 9 Sep. 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