Someone who lies constantly no matter how fruitless or insignificant the lie may be. They lie about everything. Sometimes even to try and have a "cool" persona and they may or may not believe their own lies are true, like a pathological liar.
Tanner: I live in a ten story house and have 4 maids
James: ....yeah okay.
Tanner: I knocked a girl up once and I've got a baby.
James: ...I'm sure.
Tanner: I just got into a knife fight with a man that broke into my house and I wooped his ass ..but I need stiches!
James: Yeah right. Shouldn't you be in the hospital then? let me see your wound..
Tanner: Ah, man, you don't wanna see it. its pretty gross.
James: You're a compulsive Liar