Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
illaetābĭlis (inl-), e, adj. [in-laetabilis], cheerless, joyless, gloomy, sad (poet.): ora, Verg. A. 3, 707: murmur, id. ib. 12, 619: hymen (with funestus), Sen. Troad. 861: onus, i. e. a dead child, Stat. Th. 5, 633: munus (with grave), id. ib. 3, 706.