Lewis & Short

sermōcĭnātrix, īcis, f. [sermocinator], that converses, adapted to conversation; in rhet. lang., as a part of rhetoric, a transl. of the Platonic προσομιλητική, Quint. 3, 4, 10.
In gen.: immodica, i. e. a prattler, babbler, App. M. 9, p. 224, 31.