Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
nāvĭgābĭlis, e, adj. [navigo], navigable: amnis, Liv. 38, 3: mare, id. 35, 44: fossa, Tac. A. 15, 42: litora, id. ib. 13, 53: flumen, Col. 1, 2, 3: fontes magnorum fluminum, Auct. ap. Quint. 8, 3, 76.