A large amount of powder. Usually cocaine or other drugs that are meant to be snorted. Usually lines that are laid out so that they aren't very long, but quite fat. The name comes from the lines being about the size of an infants penis.
A little itty bitty tiny penis that can barely be seen. Usually under 3-4 inches. Not something you are proud to show people. Upon being asked this question one with a baby dick will usually be hesitant out of fear from showing said baby dick.