Just a cut-and-paste from an old thread, which itself contained a cut-and-paste from an even older thread:
PRaT has been used in a non-descriptive way. But when you consider that it's really three attributes (pace, rhythm, and timing), not just one, it can be a way of more accurately describing a component's performance. Others have described it better than I can, but FWIW, here's one I posted a couple years ago:
"In short, I would say that "pace" essentially is the flow or tempo, the speed, at which music is played. Rhythm refers to the beat or time signature of the music. It's been a long time since I permanently escaped piano lessons, but I remember being told always to practice using the correct rhythm even if at a slower tempo or pace; the pace can be picked up, using the same rhythm, after better learning the notes. Timing is related to Linn's question to prospective buyers, "Do all the musicians seem to be playing together?" In other words, is their playing synchronized with the given beat."
Not to belabor the issue, but the best way for me to describe, at least to myself, the differences I heard between some 'tables I've recently owned or auditioned is to say that the Rega was exceptionally good with rhythm, a bit worse in pace, and was relatively weak in timing; the WTRP was exceptional in presentation of pace, decent with rhythm, and also had a relative weakness in timing; my LP12 was not as good as either the Rega or the WTRP in their particular areas of strength, but did all three attributes fairly well.
The most-cited reference article on attributes such as pace and rhythm has been Martin Colloms's article in Stereophile:
http://www.stereophile.com/reference/23/index.html
People who prattle on about PRaT typically consider sonic attributes such as soundstaging, transparency, imaging and extreme detail recovery to be "non-musical sonic artifacts of the recording process" (according to Jeff Day of 6 Moons), and are more focused on how well a component or system retains and communicates music's beat, rhythm, and melody.
Edit: Audio vocabulary terms, such as PRaT, are simply a means to communicate with other hobbyists about what we hear. No component is perfect, and it's perfectly fine for people to disagree about what sounds better. The terminology just helps us explain why. To take a common example, an SL1200 could be seen as either better or worse than a Rega Planar 3. I might say the Rega is better because its strengths in rhythm and pace are more important to me than the Technics's superiority in timing and speed stability; someone else could justifiably take the opposite point of view, or consider the two 'tables with completely different attributes that are more important to them. There is nothing pretentious about PRaT, it's just an attempt to describe what we hear.