Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
sententĭōsus, a, um, adj. [sententia, II. B. 2.], full of meaning, pithy, sententious (rare but Ciceron.): sententiosum et argutum genus dictionis, Cic. Brut. 95, 325.
Adv.: sententĭōsē.