Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Gărumna, Garunna, or Garon-na, ae, m. (fem., Aus. Mos. 483), = ὁ Γαρουνᾶς Strab., a river of Gaul, the Garonne, Caes. B. G. 1, 1; Mel. 3, 2, 3; 7; Plin. 4, 17, 31, § 105; Amm. 15, 11; Tib. 1, 8 (7), 11 al.