I was playing some games yesterday and at the end of the round a yellow achievement message popped up. It said [Transcendental Warrior] and the explanation was something like 'win 3 blah blah blah'. The score screen popped up before I got a chance to read it so I'm just curious what this achievement is awarded for.

Win 3 games in a row or something like that.

Yes it is simply that ^^

I looked through the service record and it is listed there. Win 3 ranked matches in a row for lvl 2. Next lvl is win 5 in a row.

Quite surprising actually - 2 months of playing MP and reaching lvl 49 and yet I only just managed to win 3 games in a row! (o.0)