Heptagon

from WordNet (r) 3.0 (2006)

heptagon
    n 1: a seven-sided polygon

from The Collaborative International Dictionary of English v.0.48

Heptagon \Hep"ta*gon\, n. [Gr. ? sevencornered; "epta` seven + ?
   angle: cf. F. heptagone.] (Geom.)
   A plane figure consisting of seven sides and having seven
   angles.
   [1913 Webster]