O / obstantĭa
noun

obstantĭa

gen. obstantiae · gender feminine · decl. 1st
a standing before; against, a resistance, hinderance, obstruction
a standing before or against, a resistance, hinderance, obstruction (only in Vitr.): terrae, Vitr. 9, 5, 4: aëris, id. 6, 1: umbrarum, id. 8, 1.