Pyr·a·mid n.
 1. A solid body standing on a triangular, square, or polygonal base, and terminating in a point at the top; especially, a structure or edifice of this shape.
 2. Geom. A solid figure contained by a plane rectilineal figure as base and several triangles which have a common vertex and whose bases are sides of the base.
 3. pl. Billiards The game of pool in which the balls are placed in the form of a triangle at spot. [Eng.]
 Altitude of a pyramid Geom., the perpendicular distance from the vertex to the plane of the base.
 Axis of a pyramid Geom., a straight line drawn from the vertex to the center of the base.
 Earth pyramid. Geol. See Earth pillars, under Earth.
 Right pyramid Geom. a pyramid whose axis is perpendicular to the base.