TBESG:ἐπιορκέωto break an oathG:V ἐπιορκέω, -ῶ (< ἐπίορκος), [in LXX: Refs I Est.1:48, Wis.14:28 * ;] to swear falsely, forswear oneself: Mat.5:33.† (AS)
ἐπίορκος epiorkos ep-ee'-or-kos From G1909 and G3727; on oath, that is, (falsely) a forswearerKJV Usage: perjured person.