Source : Webster's Revised Unabridged Dictionary (1913)

Pecopteris \Pe*cop"te*ris\, n. [NL., fr. Gr. ? to comb + ? a
   kind of fern.] (Paleon.)
   An extensive genus of fossil ferns; -- so named from the
   regular comblike arrangement of the leaflets.

Source : WordNet®

pecopteris
     n : Carboniferous fossil fern characterized by a regular
         arrangement of the leaflets resembling a comb