The Collaborative International Dictionary of English v.0.48:

Oncidium \On*cid"i*um\, n. [NL.] (Bot.)
   A genus of tropical orchidaceous plants, the flower of one
   species of which (Oncidium Papilio) resembles a butterfly.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Oncidium papilio
    n 1: orchid of South America and Trinidad having large yellow
         and reddish-brown flowers; sometimes placed in genus
         Oncidium [syn: Psychopsis papilio, Oncidium papilio]