Pentagon \Pen"ta*gon\, n. [Gr. ?; ? (see Penta-) + gwni`a angle: cf. L. pentagonium, F. pentagone.]

(Geom.) A plane figure having five angles, and, consequently, five sides; any figure having five angles.

Regular pentagon, a pentagon in which the angles are all equal, and the sides all equal.

Source: Webster's Revised Unabridged Dictionary (1913)