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

Trump has asserted multiple times in recent weeks the countries were on the cusp of a deal. —ABC News, 13 June 2026

These individuals excel at visibility, strategy decks and company-wide communications, but their actual influence ends just at the cusp of acting on it. —Dr. Adil Dalal, Forbes.com, 12 June 2026

Elon Musk is reportedly on the cusp of becoming a trillionaire and Jimmy Kimmel isn’t sure Musk is the right guy to be making that kind of cash. —Emily Zemler, Rolling Stone, 12 June 2026

For Melo, the seemingly new relationship comes at another celebratory time, with his former team on the cusp of its first NBA championship in 53 years. —Anna Lazarus Caplan, PEOPLE, 12 June 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