Oh boy. Might as well ask "what classifies asians?" cuz some ppl out there believe there's asian, and then there's asian. But here: http://en.wikipedia.org/wiki/JRPG and also look up the urbandictonary definition
1. Is it made in Japan and an RPG? Some people use this classification.
2. Is it a turn-based battle system, with all stats affecting only or almost only in-battle-related functions? This covers games like Final Fantasy, Dragon Quest, and Star Ocean, where most of, if not all stats are used only for the purposes of combat, and not like in, say, D&D, where you need to pass a strength check to bash a door down, or a dexterity check to pick a lock.
I think that accurately sums up the two possible definitions without being insulting or anything.
Edit: It can be a sore topic around here, because the die-hard defenders of either side will try to insult the other any chance they get. They're like the Sharks and the Jets, only with less singing and dancing.
It has to be extremely silly and borerline ridiculous. Usually it has to have kids as the main characters in a dated turn based battle system where you're fighting off goofy s*** like bird monsters or something. --- Intel Pentium II @ 150MHz | 32MB RAM (SIMMs) | 2GB HDD | ATI Rage Pro 3D card w/ 2MB vRAM | CD-ROM | 56k modem | Windows ME