I would actually say a person who does 1 meet still qualifies as a powerlifter. It goes to show how the term itself really doesn't hold a lot of merit, and just how ridiculous it is that people choose to give themselves the title as some sort of accomplishment.
All you need to do to be a powerlifter is be able to lift the bar for the 3 competition lifts and then do it in a meet, but a lot of internet dorks have greatly romanticized the term to mean some hardcore ammonia huffing shaved head goatee having hardass banging their head on the bar, and then they call themselves one so that they can show how hardcore they are. It's silly really.
It's the same thing with the whole "train like a powerlifter" thing. At my very first powerlifting meet, I was doing DoggCrapp beforehand. I don't think any two guys at the meet trained the same way. Hell, Jamie Lewis held the record at 181, and he just trained to be a big strong dude.
This could just be me, but it's something I've tried to hold true to myself, and not give titles where they aren't warranted. I trained boxing for years, never had a fight, and never called myself a boxer because I didn't feel it was an appropriate thing to do.
As for what to refer to yourself, you could definitely go with powerbuilder if you feel it summarizes you. I just say I'm training to get bigger and stronger, as I feel you'd be hard pressed to find someone who ISN'T doing that, haha.