Lewis Short
posca | pusca (noun F) : (, Veg. Vet. 2, 48), , perh. πόω, poto
* An acidulous drink of vinegar and water, Plaut. Mil. 3, 2, 23; id. Truc. 2, 7, 48; Cels. 4, 5 fin.; Plin. 27, 4, 12, § 29; 28, 5, 14, § 56; Scrib. Comp. 46; Suet. Vit. 12; Spart. Hadr. 10; cf.: posca, ὀξύκρατον, πόσις, Gloss. Philox.
Charlton T. Lewis, Charles Short, A Latin Dictionary