an enormous penis with lots of shaft hair. often mistaken for the trunk of a woolly mammoth.
(2 guys is a locker room)
Guy 1: hey bro, why is your left leg so much harrier than your right leg?
Guy 2: dude, you are seein it from a bad angle. thats not my left leg. its my third leg.
Guy 1: whoa! thats a mastadon!
A nickname describing a midget with an extremely large penis.
Girl 1: Hey you know peter?
Girl 2: Which one? The midget?
Girl 1: Yeah.
Girl 2: What about him?
Girl 1: He's a mastadon.
Girl 2: No Way!
A) A prehistoric wooly-mammoth.
B) One who is simular to the beast in both fur and attitude.
Bob: Hey Jerry, is that a yeti I spy?
Jerry: Bob, I can indeed see how you could be mistaken, but thats just Geoff, the local mastadon.