Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
fallācĭōsus, a, um, adj. [fallacia], deceitful, deceptive, fallacious (post-class.): argumenta (with vafra), Gell. 7, 3, 34: ambages, id. 14, 1, 34: promissio, App. M. 8, p. 205, 9.