Cusp

Cusp (Lat. cuspis, point of spear, etc.) denotes in astronomy the horn of a crescent, as for instance of the moon; in astrology the entrance of a house in the calculation of a nativity; in geometry, a point of a curve where the curve turns and goes in a reverse direction; and in architecture, the intersection of small arcs, and the figures resulting therefrom. The term is also used in anatomy, botany, and zoology.