n. In astronomy, the point or horn of a crescent, specifically of the crescent moon.n. In astrology, the beginning or first entrance of any house in the calculation of nativities.n. In geometry, a stationary point on a curve, where a point describing the curve has its motion precisely reversed.n. In architecture, an intersecting point of the small arcs or foliations decorating the internal curves of the trefoils, cinquefoils, etc., of medieval tracery; also, the figure formed by the intersection of such arcs.n. In zoöl. and anatomy:n. Any special prominence or protuberance of the crown of a tooth.n. A sharp tooth-like process on a margin or part.n. In botany, a sharp and rigid point, as of a leaf.n. One of the segments, with pointed tip, of a valve of the heart.