1 stage, period, development, step:
The boy is just going through a phase.
2 time, moment, juncture, occasion:
At this phase of the discussion, I should like to introduce a new subject
3 state, form, shape, configuration, aspect, appearance, look, condition, status:
Here is a diagram of the phases of the moon at various points in its orbit
4 facet, side, angle, viewpoint, point of view, Colloq slant:
Only one phase of the argument has so far been presented.
5 phase in. (gradually) introduce, usher in, work in, inject, insert, insinuate, include, incorporate:
The new work schedules will be phased in over the next month.
6 phase out. ease out or off, taper off, wind up, put a stop to, (gradually) eliminate, remove, withdraw, discontinue, end:
The use of non-biodegradable and non-recyclable packaging is being phased out.