Symptoms might include, holding hands, non-committal sex, spending an inordinate amount of time together, flirting on text messages.
When something's going on, but it's not dating, and it's not a booty call, it's not a serious relationship, it's not hooking up, and it's not friends with benefits... what you've got on your hands is a nonrelationship.
Chick2: Cool, so you're into him?
Chick1: Yeah, kinda.
Chick2: Is it going anywhere?
Chick1: Not really, but I want to consummate our nonrelationship.