Definition of "Phase" :

noun: (astronomy) the particular appearance of a body's state of illumination (especially one of the recurring shapes of the part of Earth's moon that is illuminated by the sun)

"The full phase of the moon."

noun: (physical chemistry) a distinct state of matter in a system; matter that is identical in chemical composition and physical state and separated from other material by the phase boundary

"The reaction occurs in the liquid phase of the system."

noun: a particular point in the time of a cycle; measured from some arbitrary zero and expressed as an angle

noun: any distinct time period in a sequence of events

verb: adjust so as to be in a synchronized condition

"He phased the intake with the output of the machine."

verb: arrange in phases or stages

"Phase a withdrawal."