D defs.my
Entry 1 sense Webster, 1913

Pentagon

/pĕn'təgän/ · Pen·ta·gon · IPA /ˈpɛn.təˌɡɑn/
01 n. A plane figure having five angles, and, consequently, five sides; any figure having five angles.
  1. 1.
    A plane figure having five angles, and, consequently, five sides; any figure having five angles.(Geom.)
Phrases & compounds
Regular pentagon — a pentagon in which the angles are all equal, and the sides all equal.