cusp

UK: /ˈkʌsp/ US: /kʌsp/ ,(kusp)

WordReference Random House Learner's Dictionary of American English © 2026

cusp /kʌsp/   n. [countable]

1. a point or pointed end, as on the crown of a tooth.
2. a point that marks the beginning of a change:
   on the cusp of a new era.

WordReference Random House Unabridged Dictionary of American English © 2026

cusp  (kusp), n. 

1. a point or pointed end.
2. Anatomy, Botany, Zoology a point, projection, or elevation, as on the crown of a tooth.
3. Mathematics Also called spinode. [Geom.] a point where two branches of a curve meet, end, and are tangent.
4. Architecture a decorative device, used esp. in Gothic architecture to vary the outlines of intradoses or to form architectural foils, consisting of a pair of curves tangent to the real or imaginary line defining the area decorated and meeting at a point within the area.
5. Astronomy a point of a crescent, esp. of the moon.
6. Astrology
   • the zodiacal degree that marks the beginning of a house or a sign.
   • Informal Terms a person born on the first day of a sign.
7. a point that marks the beginning of a change:
   on the cusp of a new era.

• Latin cuspis a point
• 1575–85

cusp′al, adj. 

Collins Concise English Dictionary © HarperCollins Publishers::

cusp / 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 a point at which two arcs of a curve intersect and at which the two tangents are coincident
5. a carving at the meeting place of two arcs
6. either of the points of a crescent moon or of a satellite or inferior planet in a similar phase
7. any division between houses or signs of the zodiac

Etymology: 16th Century: from Latin cuspis point, pointed end