O / obvŏlūtĭo
noun

obvŏlūtĭo

gen. obvŏlūtōnis · gender feminine · decl. 3rd
a wrapping round; enveloping; an envelope
a wrapping round, enveloping; an envelope (postclass.): aetherea obvolutio, Macr. Somn. Scip. 1, 11, § 12; Cael. Aur. Acut. 2, 11, 79.