Definition of phase-in:
(n) :
A distinguishable part of a sequence or cycle occurring over time.
(n) :
That which is exhibited to the eye; the appearance which anything manifests, especially any one among different and varying appearances of the same object.
(n) :
Any appearance or aspect of an object of mental apprehension or view.
(n) :
(physics) Any one point or portion in a recurring series of changes, as in the changes of motion of one of the particles constituting a wave or vibration; one portion of a series of such changes, in distinction from a contrasted portion, as the portion on one side of a position of equilibrium, in contrast with that on the opposite side.
(n) :
(chemistry) A component in a material system that is distinguished by chemical composition and/or physical state (solid, liquid or gas) and/or crystal structure. It is delineated from an adjoining phase by an abrupt change in one or more of those conditions.
(n) :
(astronomy) A particular appearance or state in a regularly recurring cycle of changes with respect to quantity of illumination or form, or the absence, of a body's illuminated disk. Illustrated in Wikipedia's article Lunar phase.