Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
immansuētus (inm-), a, um, adj. [in-mansuetus], untamed, wild, savage (poet. and in post-Aug. prose): ille ferox immansuetusque, Ov. M. 4, 237: Cyclops, id. ib. 14, 249: at tu (Borea), de rapidis immansuetissime ventis, id. H. 18, 37: trucem atque immansuetum bovem caedimus, Sen. de Ira, 1, 15: ingenium immansuetum ferumque, Ov. M. 15, 85: quid immansuetius? Sen. Cons. ad Helv. 6.