When you
mean to do something really obvious but then you forget what you were doing and end up doing something something completely different. i.
e, when you have a wrapper in
one hand and food in the other, and throw away the food and try to eat the wrapper.
Brain Fart:
Person
1: Man, I had such a brain fart today.
Person 2: What did you do?
Person
1: I was holding
food and a wrapper and threw away the food and tried to eat the wrapper.