noun

• any distinct time period in a sequence of events
  "we are in a transitional stage in which many former ideas must be revised or rejected"
• (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"
• a particular point in the time of a cycle; measured from some arbitrary zero and expressed as an angle
• (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"

verb

• arrange in phases or stages
  "phase a withdrawal"
• adjust so as to be in a synchronized condition
  "he phased the intake with the output of the machine"