cusp / kəsp/ • n. 1. a pointed end where two curves meet, in particular: ∎  Archit. a projecting point between small arcs in Gothic tracery. ∎  a cone-shaped prominence on the surface of a tooth, esp. of a molar or premolar. ∎  Anat. a pocket or fold in the wall of the heart or a major blood vessel that fills and distends if the blood flows backward, so forming part of a valve. ∎  Math. a point at which the direction of a curve is abruptly reversed. ∎  each of the pointed ends of a crescent, esp. of the moon.2. Astrol. the initial point of an astrological sign or house: he was Aries on the cusp with Taurus. ∎ fig. a point between two different situations or states, when a person or thing is poised between the two: those on the cusp of adulthood.DERIVATIVES: cus·pate / ˈkəspət; -ˌpāt/ adj.cusped adj.cus·pi·date / ˈkəspəˌdāt/ adj.

cusp. Point made by the intersection of two curved lines or members, e.g. the projecting point between the small arcs or foils in Gothic tracery, or the enrichment on the intrados of a Gothic arch provided by foliation, the curves of which touch the inner edge of the main arch (cusped arch).

cusp
1. A sharp raised protuberance on the surface of a molar tooth. The cusps of opposing molars (i.e. on opposite jaws) are complementary to each other, which increases the efficiency of grinding food during chewing.

2. A flap forming part of a valve.

cusp (kusp) n.
1. any of the cone-shaped prominences on the teeth, especially the premolars and molars.

2. a pocket or fold of the membrane lining the heart or of the layer of the wall of a vein, several of which form a valve. When the blood flows backwards the cusps fill up and become distended, so closing the valve.

cusp (astrol.) entrance of a house XVI; point, apex XVII. — L. cuspis, -id- point, pointed weapon.
So cuspidate(d) sharp-pointed. XVII. — pp. of L. cuspidāre, see -ATE 2.