Noun-An abnormally small penis. Usually under 5 inches. The name insinuates its cuteness.
Brenda-"Awww, look at the lil' peter petweeter. It's so cute!"
Brad-"I would prefer if you didn't call Mr. Bigglesworth cute."
(Note, talking baby talk to a slong is usually considered a no-no for fear of insulting its owner, yet always tempting.)