Aw snap is used when something goes wrong, such as if there is a Fight and someone just got "told".
You say:I Love you Kira
She says:I Don't love you
I say: Aw Snap!
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Ethan was trying to access google drive to do his assignment and was provided with an Aw, Snap!
This can be used as if you have forgotten something.
Aw snap! I was supposed to go pick up my momma from work 3 hours ago.