Source : Webster's Revised Unabridged Dictionary (1913)

Butterwort \But"ter*wort`\, n. (Bot.)
   A genus of low herbs ({Pinguicula}) having simple leaves
   which secrete from their glandular upper surface a viscid
   fluid, to which insects adhere, after which the margin
   infolds and the insects are digested by the plant. The
   species are found mostly in the North Temperate zone.

Source : WordNet®

butterwort
     n : any of numerous carnivorous bog plants of the genus
         Pinguicula having showy purple or yellow or white flowers
         and a rosette of basal leaves coated with a sticky
         secretion to trap small insects