An extreme case of burning hemorrhoids in which the inside of the anus is so elongated that it hangs down like an elephant's proboscis. And like the real elephant's trunk, it is extremely sensitive and can smell terrible. Unlike the real elephant's trunk, it is not strong enough to rip the branches off a tree.
Guy #1: Man, I biked 5 hours today on my Grandma's old Schwinn.
Guy #2: Ouch! That must have really been painful on your arse.
Guy #1: You said it. I got an elephant trunk so long it's wrapped around my junk.