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

Where to Stay The Hedges Inn The owners of The Colony Hotel in Palm Beach have refreshed The Hedges Inn, a beloved landmark right on the cusp of East Hampton town. —Elise Taylor, Vogue, 13 June 2025

Think about last year’s BYU team that went 10-2 but didn’t have a chance at an at-large bid while three loss SEC teams like Alabama, Ole Miss and South Carolina were right on the cusp of getting into the field. —Steven Johnson, Fort Worth Star-Telegram, 12 June 2025

Shai Gilgeous-Alexander was named Western Conference finals MVP. Oklahoma City advanced to the NBA Finals for the first time since Kevin Durant, Russell Westbrook and James Harden took the 2012 team to the cusp of the Promised Land. —Tony Jones, New York Times, 29 May 2025

Late goals by Seth Jones and Carter Verhaeghe less than two minutes apart lifted the Cats to the cusp of advancing). —Greg Cote, Miami Herald, 29 Apr. 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