Source : Webster's Revised Unabridged Dictionary (1913)

Frogbit \Frog"bit`\, n. (Bot.)
   (a) A European plant ({Hydrocharis Morsus-ran[ae]}), floating
       on still water and propagating itself by runners. It has
       roundish leaves and small white flowers.
   (b) An American plant ({Limnobium Spongia}), with similar
       habits.

Source : WordNet®

frogbit
     n : European floating plant with roundish heart-shaped leaves
         and white flowers [syn: {frog's-bit}, {Hydrocharis
         morsus-ranae}]