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

This will be Andoni Iraola’s final home game in charge, a farewell for a manager who has taken Bournemouth to the cusp of Champions League football despite selling the entire back line in the summer and, in January, losing what was arguably the league’s standout player of the season. —Sukhman Singh, New York Times, 16 May 2026

The coffee influence comes from barrel finishing rather than direct flavoring or infusion, placing the rum on the cusp between barrel-finished and flavored rums. —Joseph V Micallef, Forbes.com, 16 May 2026

SpaceX is on the cusp of launching its gargantuan Starship rocket for the first time in 2026. —Eric Lagatta, USA Today, 15 May 2026

The plan, previously spearheaded by United Way of Greater Charlotte, seeks to help people on the cusp of or already experiencing homelessness. —Desiree Mathurin, Charlotte Observer, 12 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