'Undecagon' definitions:

Definition of 'undecagon'

(from WordNet)
noun
An eleven-sided polygon

Definition of 'Undecagon'

From: GCIDE
  • Undecagon \Un*dec"a*gon\, n. [L. undecim eleven + Gr. ? an angle.] (Geom.) A figure having eleven angles and eleven sides. [1913 Webster]