"Potential Hook Up". Used in reference to a person who may be interested in hooking up with you or someone you know. There is much uncertainty when it comes to deciding whether someone may be a PHU, but clues include: level of flirting between the two, phone/text conversations and interest shown through facebook activity such as wall posts or excessive commenting on one's pics. PHU's may also be a more short-term and random occurrence, stemming from consumption of intoxicants at social events.
"I've been texting him all week and he 'liked' at least 5 of my profile pics. What do you think?"
"I think he's a PHU. Good luck."
"We're going to leave the party now"
"Okay, you guys go. Based on Pat and I's interaction as pong partners, I think he's a PHU."
"If that PHU were to happen, it would be so GFC
"Yeah I know, he's such a GC