Lewis & Short

gymnăsĭarchus, i, m., = γυμνασίαρχος, the master of a gymnasium, a gymnasiarch, Cic. Verr. 2, 4, 42, § 92; Sid. Ep. 2, 2; Val. Max. 9, 10, 2 ext.
Also, gym-năsĭarcha, ae, m., = γυμνασιάρχης, Val. Max. 9, 12, 7 ext.; Inscr. Grut. 465, 2.