The Collaborative International Dictionary of English v.0.48:

Ranunculus \Ra*nun"cu*lus\ (r[.a]*n[u^][ng]"k[-u]*l[u^]s), n.;
   pl. E. Ranunculuses (r[.a]*n[u^][ng]"k[-u]*l[u^]s*[e^]z),
   L. Ranunculi (-l[imac]). [L., a little frog, a medicinal
   plant, perhaps crowfoot, dim. of rana a frog; cf. raccare to
   roar.] (Bot.)
   A genus of herbs, mostly with yellow flowers, including
   crowfoot, buttercups, and the cultivated ranunculi
   (Ranunculus Asiaticus, Ranunculus aconitifolius, etc.) in
   which the flowers are double and of various colors.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Ranunculus
    n 1: annual, biennial or perennial herbs: buttercup; crowfoot
         [syn: Ranunculus, genus Ranunculus]