The Collaborative International Dictionary of English v.0.48:

Plenicorn \Ple"ni*corn\ (pl[=e]"n[i^]*k[^o]rn), n. [L. plenus
   full + cornu horn.] (Zool.)
   A ruminant having solid horns or antlers, as the deer.
   --Brande & C.
   [1913 Webster]