cusp

American  

[kuhsp] / kʌsp /

noun

1. a point that marks the beginning of a change.

   Our nation is on the cusp of a new era.

   Some of our machines are now getting very old and are on the cusp of being replaced.

2. a point or pointed end.

   The sharp cusp of the mountain pierced through the thick clouds.

3. Anatomy, Zoology, Botany. a point, projection, or elevation, as on the crown of a tooth.

4. Also called spinode.  Geometry. a point where two branches of a curve meet, end, and are tangent.

5. Architecture. a decorative device consisting of a pair of curves that are tangent to a real or imaginary line defining the area being decorated, and meet at a point within that area: used especially in Gothic architecture to vary the outlines of intrados or to form architectural foils.

6. Astronomy. a point of a crescent, especially of the moon.

7. Astrology.

   1. the zodiacal degree that marks the separation between consecutive houses or signs.

      Those born on the Cancer/Leo cusp have the vitality and ambition to be successful in their creative endeavors.

   2. Informal. a person born during a time when the sun is at the very end of one sign or at the very beginning of another.

      Virgos and Virgo cusps tend to be shy and somewhat nervous, and they may be undemonstrative.

      I'm an Aries/Pisces cusp with Capricorn rising.

---

cusp British  

/ kʌsp /

noun

1. any of the small elevations on the grinding or chewing surface of a tooth

2. any of the triangular flaps of a heart valve

3. a point or pointed end

4. Also called: spinode.  geometry a point at which two arcs of a curve intersect and at which the two tangents are coincident

5. architect a carving at the meeting place of two arcs

6. astronomy either of the points of a crescent moon or of a satellite or inferior planet in a similar phase

7. astrology any division between houses or signs of the zodiac

---

Usage

What is a cusp? Most often, cusp is used figuratively to mean a turning point or a point that marks a new beginning, as in Jorge was on the cusp of a scientific breakthrough when his grant money ran out. Literally, a cusp is a point or pointed end, as with the peak of a mountain. Cusp also has several specialized uses, too. In anatomy and related fields, a cusp is the tip, as on a tooth. Your dentist might refer to your cuspid and bicuspid teeth. These are teeth with one point and two points, respectively. In architecture, a cusp is the apex of two curves that come to a point, found especially in Gothic arches. And in astronomy, a cusp is the point of a crescent, such as with the moon. Example: We are on the cusp of a great discovery.

Other Word Forms

• cuspal adjective

Etymology

Origin of cusp

First recorded in 1575–85, from Latin cuspis “a point”

Explanation

A cusp in geometry is the point where two curves meet. It's a kind of transition. If you're on the cusp of manhood, you’re not quite grown up, but you’re definitely not a little boy anymore either. The word comes from Latin cuspis, "point." You'll see lots of cusps in Gothic churches — a point where two arches meet, or where decorative curves meet to form a point. The little points that stick out on the surface of your teeth that are flat on top — the ones you use for grinding — are also called cusps. Those teeth right behind your canine teeth but before your molars have two cusps, and they're called bicuspids.

Example Sentences

This has left the pioneering cryptocurrency on the cusp of a breakout that could take its price back toward six-figure territory, analysts said.

From MarketWatch • Apr. 14, 2026

And the attention on space is intense right now, with the huge succesof NASA’s Artemis II mission and SpaceX on the cusp of an initial public offering.

From Barron's • Apr. 13, 2026

When Edison had his famous “lightbulb moment” in 1879, British scientist Joseph Swan was also on the cusp of inventing an incandescent lightbulb using similar techniques.

From The Wall Street Journal • Apr. 5, 2026

The analysis showed that this cusp is consistently shifted to one side.

From Science Daily • Apr. 3, 2026

It was midnight, the cusp of another scary and vivid childhood memory.

From "A Deadly Wandering: A Mystery, a Landmark Investigation, and the Astonishing Science of Attention in the Digital Age" by Matt Richtel