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

For many schools, that means expanding technical education classes, building partnerships with local businesses, and getting creative with transporting teens — some just on the cusp of learning to drive — to part-time work. —Carley Lanich, IndyStar, 10 Feb. 2026

The Patriots finished the season 14-3, Maye passed for more than 4,000 yards, 31 touchdowns and – while his playoff performances haven’t exactly been outstanding – Maye has brought his team to the cusp of yet another Patriot Super Bowl title. —Kyle Feldscher, CNN Money, 4 Feb. 2026

Today, Glenn stands on the cusp of becoming a legend. —Marcus Thompson Ii, New York Times, 4 Feb. 2026

Like Lincoln in the Bardo, Saunders’s other novel, Vigil is set on the spooky cusp between life and death. —Julius Taranto, The Atlantic, 27 Jan. 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