Quick Definition
στρατοπεδάρχης, ου, ὁ n.m. commander of the Roman emperor’s body-guard
Strong's Definition
a ruler of an army, i.e. (specially), a Prætorian præfect
Derivation: from G4760 (στρατόπεδον) and G757 (ἄρχω);
KJV Usage: captain of the guard
Thayer's Greek Lexicon
στρατοπεδάρχης, -ov, ὁ, (στρατόπεδον and ἄρχω), [cf. B. 73 (64)7; a. the commander of a camp and army, a military tribune: Dion. Hal. 10, 36 ; Leian. hist. conser. 22; [Joseph. b. j. 2, 19, 4]. b. Praetorian prefect, commander of the praetorian cohorts, i. 6. captain of the Roman emperor’s body-guard: Acts xxviii. 16 [LT Tr WH om. the cl., see Abbot in B.D., Am. ed., s. v. Captain of the Guard]. There were two praetorian prefects, to whose custody prisoners sent bound to the emperor were consigned: Joseph. antt. 18, 6,6; Plin. epp. 10, 65 (57). [See B. D. Am. ed. u.s.; Bp. Lghtft. on Phil. p. 7 sq.]
Mounce Concise Greek Dictionary
Abbott-Smith Greek Lexicon
*† στρατοπέδ-αρχος (Rec. -ης), -ου, ὁ
(< στρατόπεδον, ἄρχω), a military commander, esp. the Pretorian prefect: Ac 28:16 (WH, om.).†
Moulton & Milligan — Vocabulary of the Greek NT
στρατοπεδάρχης. Mommsen :(Sz¢zn2gsb. d. preussischen Akademie, 1895, No. XXVII) argues that this word, which occurs in the TR of Ac 2815, means there prznceps peregrinorum, but in P Lond 196° (c, A.D. 138-161) (=II. p. 153) the editor prefers to understand the title as = princeps castrorum, and compares Mommsen /.c. p. 498. See his note ad /. from which the foregoing is derived. We may add references to Vett. Val. p. στρατοπεδάρχας ναυτικῶν Te καὶ πεζικῶν ἄρχοντας, and to OGZS 605° (v/A.D.). 761% ποιοῦσι
Liddell-Scott-Jones — Greek-English Lexicon
στρατοπεδάρχης (stratopedarchēs) — commander. στρᾰτοπεδ-άρχης, ου, ὁ, military commander, [Refs 1st c.BC+]; = praefectus castrorum, [Refs 2nd c.AD+]