R / rŏtundātĭo
noun

rŏtundātĭo

gen. rŏtundātōnis · gender feminine · decl. 3rd
a making round; a rounding
a making round, a rounding: linea rotundationis, i. e. the circumference, Vitr. 1, 6 fin.; 3, 1; 10, 11.