Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
importŭōsus (inp-), a, um, adj. [2. in-portuosus], without a harbor: mare, Sall. J. 17, 5: laeva inportuosa Italiae litora, Liv. 10, 2, 4; Tac. A. 4, 67: litus, Plin. Ep. 6, 31, 17: insula importuosissima omnium, Plin. 4, 12, 23, § 73.