P / prō-sŏcer
noun

prō-sŏcer

gen. prō-sŏcĕri · gender masculine · decl. 2nd
a wife's grandfather
a wife's grandfather: cuique senex Nereus prosocer esse velit, Ov. H. 3, 74: uxor, et nurus, et pronurus, viro, et socero, et prosocero furtum facere possunt, Dig. 25, 2, 15: erum cum prosocero meo, Plin. Ep. 5, 14 (15), 8.