As a verb, it is used to describe a future action in which one exceeds the normal outcome. For example: If you are about to eat more food than average, you might say "I am going to get big in the kitchen." Can be used in a variety of ways: in reference to eating, fighting, taking a test, anything.
Somebody just got big in the bathroom.
I am going to get big in the andrology lab today.
Get big with that panhandler.
I'm hungry as shit, let's get big.