The Collaborative International Dictionary of English v.0.48:
Ranula \Ran"u*la\ (r[a^]n"[-u]*l[.a]), 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. [1913 Webster]WordNet (r) 3.0 (2006):
ranula n 1: a cyst on the underside of the tongue