It’s a concept held onto by Linnies (fans of the Linn Sondek turntable), now applied to even electronics. Art Dudley and Herb Reichert apply the term in their amp and pre-amp reviews in Stereophile, claiming something about the electronics effects the perceived timing of the playing of musicians. It’s such a purely subjective construct, with no way to quantify the degree involved.
I’m sure most here have no problem with the idea of tables and speakers---components with moving parts---being able to effect timing, but how would a pre-amp or amp do that? Art seems to believe electronics can "hold onto" a note too long, or can effect the "attack" (leading edge of a transient), thus effecting the timing of music.
Even more subjective is this new idea being used, that of a component being able to reproduce the "intent" of a musician. Try to quantify THAT!