I'd like to believe the definition of a shower is one that doesn't grow that much when an erection is obtain. People who grow less than 1.5" are more showers, because what you see is pretty much what you get.
A grower is someone who grows 2"+ when an erection is obtain.
People are "both" when have a significant sized flaccid and grow 2"+. But I think if you're at a significant size flaccid you could never be a true "grower".
Like soft I'm a little under 5", but I grow to 8".