cusp
Pronunciation: /kʌsp/
noun
- 1a pointed end where two curves meet, in particular:
- Architecture a moulded projection at the point of a small arch in Gothic tracery.
- a cone-shaped prominence on the surface of a tooth.
- Anatomy a pocket or fold in the wall of the heart or a major blood vessel that fills and distends if the blood flows backwards, so forming part of a valve.
- Mathematics a point at which the direction of a curve is abruptly reversed.
- each of the pointed ends of the crescent moon.
- Botany a sharp rigid point of a leaf.


Origin:
late 16th century (in cusp (sense 2)): from Latin cuspis 'point or apex'