A long and girthy penis. Like a baby arm in length, but also extremely thick.
Pericles: So I heard you got his big donny last night. I told you it was a baby arm!
Carin: You weren't kidding that his cock is huge! You should know, though, that it is really a baby thigh. I think I might be permanently stretched out and need a daddy stitch. AND I had to stretch my mouth so wide to give him a bj that my jaw now pops.