Buttercup \But"ter*cup`\, n. (Bot.) A plant of the genus Ranunculus, or crowfoot, particularly R. bulbosus, with bright yellow flowers; -- called also butterflower, golden cup, and kingcup. It is the cuckoobud of Shakespeare.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Cuckoobud \Cuck"oo*bud"\ (k??k"??-b?d`), n. (Bot.) A species of Ranunculus (R. bulbosus); -- called also butterflower, buttercup, kingcup, goldcup. --Shak.

Source: Webster's Revised Unabridged Dictionary (1913)