U / ustĭo
noun

ustĭo

gen. ustōnis · gender feminine · decl. 3rd
a burning; searing; cauterizing
a burning, searing, or cauterizing (post-Aug. and very rare): si costa cariosa est, inutilis ustio, Cels. 8, 2 fin.: quaedam ustione sanantur, Plin. 34, 15, 44, § 151: vehementior sinapis, id. 20, 22, 87, § 239.