Phase  —n. 1 stage in a process of change or development. 2 each of the aspects of the moon or a planet, according to the amount of its illumination. 3 physics stage in a periodically recurring sequence, esp. The wave-form of alternating electric currents or light. —v. (-sing) carry out (a programme etc.) In phases or stages.  phase in (or out) bring gradually into (or out of) use. [greek phasis appearance]