An abbreviation for Phantasy Tour, a message board created by and maintained by dirty Phish fans. There are other subsections in PT, such as Phantasy Bisco, Phantasy moe., etc.. But Phantasy Phish is the only one that really matters. It's addictive, pointless, and immature...but is one of the highest frequented free message boards on the web.
"I spent nearly 4 hours on PT this morning."
Did you hear the new Trey rumor from PT yesterday?"