How would you define PRaT ?

Howdy Y'all,

this question has probably been asked before someday,but...
I know that Naim is well known for its PRaT,but how would you guys describe things like Pace, Rythm and timing ?
When I listen to my Nait-2 and shortly after that switch to my (previous amp) Cyrus III I sure do notice a difference,and mostly I prefer the Nait-2 for it's openness, natural mids and detail (depending on speakers and music) but I honestly find it hard to hard to understand what the PRaT is about ?

I'll try to explain what I feel when (for example) comparing a Nait-2 to a Cyrus III:

With simpeler styles of music (preferably acoustic) I feel that the Nait is more open in de mids and the intsruments sound more natural and it's easy to focus completely on the music.
The Cyrus III 'sounds' good but has more or less a kind of 'HiFi' sound. A little more synthetic,imo (hope I used the right words)
In complex,dynamic pieces of music the Cyrus III shows it has more power in reserve and goes louder without any distress.
(now, this comparing I did with a CDX and a pair of Sonus Faber 'Concertino'(88db 'home'-series)

So,...Who can tell me what PRaT means ?
(is it perhaps the 'air-guitar' feeling when some uptempo music is played ?)

Greetings from a sunny Holland,
Alco