1. To play in a whimsical manner.
2. To mess around with; play around with.
1. See those kids over there? They sure are doofin' it up!
a. Ay Dog, you better not be doofin' around with my sister! Cuz if I find out...
b. Hey man, I thought you said that there will be girls at this spot. Why you gotta be doofin' me like that? I hate it when you doof about sh!t like that!