In DJing, phrasing, also called stage matching, refers to alignment of phrases of two tracks in a mix.
This allows the transition between the tracks to be done without breaking the musical structure.
Phrasing is an aspect of beatmixing, not a separate technique.
Because most music has a 4/4 time signature and a simple structure of 16-bar phrases, to align the phrases of two tracks it is often enough to start the track to be mixed in at a phrase boundary in the track currently playing.
Careful phrasing can produce a seamless mix by making the breaks in two tracks coincide, or aligning the break in one track with the start of the beat in the other.