pyramid

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. 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. The game of pool in which the balls are placed in the form of a triangle at spot.