The Collaborative International Dictionary
Phase in \Phase" in`\ (f[=a]z" [i^]n`), v. t. To begin an activity or to incorporate new elements or replace older elements of an activity in steps, or by degrees.
Wiktionary
vb. To introduce something little by little
WordNet
v. introduce gradually [ant: phase out]
Usage examples of "phase in".
Dad still spent most of each dark phase in town, working on a part time basis, but that was quite as much because he was interested in the manufacturing project as it was to help pay off our debts.
Perhaps in the phase in which she now was she could not have been convinced, would not have listened to proof, would not have cared.
I was midway through my Army service, separated from the nut I was later to divorce, going through a strange phase in my writing, hating every minute of the waking hours.
Had he been 'be objective of a single phase in the Kobra mission like Heinrich Fogel or was he the objective for the whole mission?
It may thus be said to have initiated a new phase in Buddhist philosophy and religion.
But he'd never know, because there's always a phase in the mission when you're suddenly and critically in need of Control direction on a major issue and can't get it or don't want to.
My superiors believe that there has been an attempt made to obliterate the Hobart Phase in regard to him -- a clear violation of law, and one posing a great danger to society.