Webster's Revised Unabridged Dictionary · 1913

Pentagon

Pentagon , noun

[Greek penta`gwnon; penta- (see Penta-) + gwni`a angle: compare Latin pentagonium, French pentagone.]

(Geometry) A plane figure having five angles, and, consequently, five sides; any figure having five angles.
Collocations (1)
Regular pentagon , a pentagon in which the angles are all equal, and the sides all equal.