pentagon Meaning, Definition & Usage

  1. noun a government building with five sides that serves as the headquarters of the United States Department of Defense
  2. noun the United States military establishment
  3. noun a five-sided polygon

WordNet

Pen"ta*gon noun
Etymology
Gr. (see Penta-) + gwni`a angle: cf. L. pentagonium, F. pentagone.
Definitions
  1. (Geom.) A plane figure having five angles, and, consequently, five sides; any figure having five angles.

Webster 1913