Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
gypso, āvi, ātum, 1, v. a. [gypsum], to cover or coat with gypsum, to plaster: opercula, Col. 12, 39, 2: vas, id. ib. 43.
Poet.: gypsati pedes, the feet of a prisoner marked with gypsum, to show that he was to be sold for a slave, Tib. 2, 3, 60; Ov. Am. 1, 8, 64.
Hence, gypsātus, a, um, P. a., covered or coated with gypsum: quibus illa (Medea) manibus gypsatissimis persuasit, ne sibi illae vitio verterent, quod abesset a patria, with hands thickly coated with gypsum (of actors who played women’s parts), Cic. Fam. 7, 6, 1; Petr. 34.