Used as an exclamation for when you hear someone tell you something, and you know it is complete bulls**t. Either from the unlikelihood of the whole story, or if you were there and you know whatactually happened.
Also could replace "Ya Right!" or a sarcastic "Okay!" in your everyday speech.
Don, you're such a yogogorilla. You shouldn't dump the juice of your manwhistle into that british, who is from the same country as you incase you didnt notice, lass while she's passed outon the couch in britan.