Source : Webster's Revised Unabridged Dictionary (1913)

Ranula \Ran"u*la\, n. [L., a little frog, a little swelling on
   the tongue of cattle, dim. of rana a frog.] (Med.)
   A cyst formed under the tongue by obstruction of the duct of
   the submaxillary gland.

Source : WordNet®

ranula
     n : a cyst on the underside of the tongue
     [also: {ranulae} (pl)]