Lewis Short
(adj.adv.) : sŭperlātīvus, a, um, adj.superlatus;
* In gram.: nomen,superlative, in the superlative degree,Charis. p. 87 P.; Prisc. p. 605 ib.
* Hyperbolic, exaggerated: sententiae,Isid. 2, 21, 16. — Hence, adv.: sŭperlātīvē, superlatively, in the superlative, Charis. p. 87 P.
Charlton T. Lewis, Charles Short, A Latin Dictionary