Lewis & Short

ĕphēbus, i (gen. plur. contr. ephebūm, Stat. Th. 4, 232), m., = ἔφηβος, a male Greek youth from 18 to 20 years of age (cf.: puer, adolescens, juvenis, adultus, pubes), Ter. Eun. 5, 1, 8; Cic. Fl. 21, 51; id. N. D. 1, 28, 79; Suet. Aug. 98; id. Ner. 12; Hor. Ep. 2, 1, 171; Ov. A. A. 1, 147 al.: is postquam excessit ex ephebis (after the Gr. ἐξελθεῖν ἐξ ἐφήβων), i. e. after he had come to the age of manhood, Ter. And. 1, 1, 24 Ruhnk. (also cited in Cic. de Or. 2, 80, 327).