dodecagon

from WordNet (r) 3.0 (2006)

dodecagon
    n 1: a twelve-sided polygon

from The Collaborative International Dictionary of English v.0.48

Dodecagon \Do*dec"a*gon\, n. [Gr. ? twelve + ? angle: cf. F.
   dod['e]cagone.] (Geom.)
   A figure or polygon bounded by twelve sides and containing
   twelve angles.
   [1913 Webster]