of or pertaining to a circuit, system, or device that is energized by three electromotive forces that differ in phase by one third of a cycle or 120°.
2.
having three phases.
Origin
1890-95
British Dictionary definitions for three-phase
three-phase
adjective
1.
(of an electrical system, circuit, or device) having, generating, or using three alternating voltages of the same frequency, displaced in phase by 120°