to leave or walk/drive away; refers to the appearance of one diminishing in stature when walking away from an observer, or appearing to "get smaller"
I'm about to get small and go to my friend's house.
Similar to the usage of do work, get small can mean a number of things depending on how you use it. Perhaps when you want to get drunk. Maybe when you want to go ride a bike. Maybe when you are going to class.
1. You guys ready to get small tonight?
2. Hey bra lets go grab some food; im so small right now.
3. Did you hear that new Senses Fail song? It's so small.