a person who has sexual feelings towards men women and dogs. they enjoy saying how much they want a dog. they often deny this. often theis people own a dog.
colin- "i so want that dog"
john- "where do u want that dog? in the ass"
colin- "no im straight"
john- "then why do u shag your dog?"
colin- "i cant help it i need help"
john- "yes..yes u do"
bob- "what wrong with that guy"
john- "oh hes just trisexual"
A female or male, usually a female though, who claims to either have previously or is willing to currently try any sexual act, at least once. Also called a trysexual.
Male to female: So how do you feel about Menage a trois?
female to male: Well, I'm a tri-sexual, so i'll try anything once! And if i like it...well, then you can just call me a freak.
Julie- "Wow, he's really cute."
Anne- "Oh yeah, he is."
~fifteen minutes later~
Julie- "Omigosh. Check out that chickover there!"
Anne- "Wait... I thought you were straight. You're bi?"
Julie- "Nope. I'm just trisexual."