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

• brink
• edge
• point
• threshold
• verge

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

Right on the cusp of Aspen Mountain is the luxurious and sprawling St. Regis resort which, in the summer, has the best pool in town. —Elise Taylor, Vogue, 8 Apr. 2025

These teeth reveal distinct cusp patterns that are virtually identical to those of parapithecids and eosimiids, families of African primates that lived over 30 million years ago. —Scott Travers, Forbes, 11 Jan. 2025

Leading the newcomers to the Paris schedule is Alaïa, who will show on March 4 at 7 p.m., after previously showing at the cusp between men’s and couture weeks. —Lily Templeton, WWD, 3 Feb. 2025

And people born on the cusp of one generation or the other like to debate their affiliation. —Savannah Kuchar, USA TODAY, 11 Feb. 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