A jerph is someone who cuts in a conversation, and preteds to know whats going on, usually seeing no harm in what they are doing. Also used as an insult to somebody who acts like a jerph.
Steve: Yo Scotty, did you hear I got some new tires on my bike.
Scott: What on your Super8?
Ryan: Oh thats Killer
Steve: Take off Ryan.
Scott: Get outta here jerph.
-A typical converstion involving a jerph would be more harsh that this because jerphs really piss ppl