Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
ventrĭōsus, a, um, adj. [venter], having a large belly, big-bellied, pot-bellied: homo, Plaut. As. 2, 3, 20; id. Merc. 3, 4, 54; id. Ps. 4, 7, 120; id. Rud. 2, 2, 11.
In the collat. form ventrŭōsus, bellying out: ventruosa ac patula dolia, Plin. 14, 21, 27, § 134; and ventrōsus, Cassiod. in Psa. 72.