I was going to say that I would think it was a typo for "pyro."
I've been looking at this for a while, trying to work out why the word rang a bell for me, a very specific "I've heard this in some kind of American context where it was presented as an ususual word" bell.
Ten minutes of frustrated head-scratching later, I worked it out. I have heard it in an American teen movie, which is interesting considering we mostly seem to be agreeing that it's rather obscure - but then the context seems to support that to some extent, when you look a little closer.
The movie in question is "Bring it On" (about teenage cheerleaders) and the quote goes:
Darcy: Bring on the tyros, the neophytes and the dilettanti.
Jan: S.A.T.s are over, Darcy.
Darcy: And you're still jealous of my score.
I tried to find a video clip but can't, which is a shame as the context is that the cheerleader named Darcy had created her own cheer to help her learn a long list of 'hard' words for her SAT exams, and the cheer itself is well worth watching for both comedy and educational value. If I remember correctly you only see part of it in the film itself but the whole things is on the DVD as an extra, and probably therefore on youtube somewhere.