Lewis & Short

văcīvus or vŏcīvus (so always in Plautus; cf. Trin. prol. 11 Brix; Ritschl, Nov. Exc. I. p. 59 sq.), a, um, adj. [vaco], empty, void (ante-class.); absol.: aedes facere alicui, Plaut. Cas. 3, 4, 6: aedes aurium, id. Ps. 1, 5, 54; for which, aures, id. Cas. prol. 29; id. Trin. prol. 11.
With gen.: valens afflictet me vocivum virium, i. e. destitute of strength, powerless, Plaut. Bacch. 1, 2, 46: tempus laboris, Ter. Heaut. 1, 1, 38.
Adv.: văcīvē, at leisure, leisurely: libellum perlegere, Phaedr. 5, praef. 14.