Pyramid (n.) : 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.
Pyramid (n.) : 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.
Pyramid (n.) : The game of pool in which the balls are placed in the form of a triangle at spot.