This is the definition accorfing to urban dictionary:
The male human when erect is one of two sizes. Long or rather short. Most males grow to an extended length after a rush of blood enters the penis. This person is a GROWER.
Some males will not grow in length when peaking an erection. These males are as long as they are gonna get, either stiff, or soft like a bunny. They are known as SHOWERS, as they show their goods in the beginning.