[1] : The Collaborative International Dictionary of English v.0.48

cuckoobud \cuck"oobud"\ k??k"??-b?d`, n. bot.
   a species of ranunculus ranunculus bulbosus; -- called
   also butterflower, buttercup, kingcup, goldcup.
   --shak.
   1913 webster
see also:
ranunculus ranunculus bulbosus butterflower buttercup kingcup goldcup 

[2] : The Collaborative International Dictionary of English v.0.48

buttercup \but"tercup`\, n. bot.
   a plant of the genus ranunculus, or crowfoot, particularly
   ranunculus bulbosus, with bright yellow flowers; -- called
   also butterflower, golden cup, and kingcup. it is the
   cuckoobud of shakespeare.
   1913 webster
see also:
ranunculus ranunculus bulbosus butterflower golden cup kingcup cuckoobud 

[3] : WordNet (r) 2.0

ranunculus bulbosus
     n : perennial old world buttercup with golden to sulphur yellow
         flowers in late spring to early summer; naturalized in
         north america syn: common buttercup
see also:
common buttercup 

Ranunculus >> R Words
Ranunculus, definition of term: Ranunculus
ranunculus_pag1.html