Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
ex-somnis (exomn-), e, adj. [somnus], sleepless, wakeful, watchful (poet. and in post-Aug. prose; cf.: insomnis, vigil, vigilans): vir, Vell. 2, 88, 2: (Tisiphone) Vestibulum exsomnis servat noctesque diesque, Verg. A. 6, 556; Sil. 9, 5: animo exsomnis, Vell. 2, 127 fin.