Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
1. grossus, i, m. and f., an unripe fig, Cato, R. R. 94; Cels. 5, 12; Plin. 23, 7, 63, § 125; 17, 27, 43, § 254.
2. grossus, a, um, adj. [kindred with crassus], thick (late Lat.): virga, Cassiod. Hist. Eccl. 10, 33.
Comp.: vestis grossior, Sulp. Sev. Dal. 1, 21; Vulg. Ezech. 41, 25; 1 Reg. 12, 10; 2 Chron. 10, 10.
Sup., Cassiod. in Psa. 29, 12; cf.: grossus παχύς, Gloss. Philox.
Hence, adv. only comp.: gros-sĭus, more roughly: definire, Aug. de Duab. Anim. 11, 15.