When you are attempting to remember something very obvious, someting that you know you should know. This feeling often leads to head banging and hair pulling.
bobby raised his hand to answer the teacher's question only to find that he had had a brain fart, and he was unable to answer 2+2.
by David Peterle December 11, 2006
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.
by nv2001 February 9, 2015
A sudden and involuntary (although depending on the source, not altogether unexpected) release of ignorance.
Jeff had a brain fart and locked his keys in his car (again!)
by GTOgirl July 13, 2009
Blurb in your head outta nowhere, train of thought goes weird
Whoops sorry Brain Fart
by Emily March 12, 2005
When something you were going to say but the thought escaped your memory and doesn't return.
I have an idea but now I don't remember what it was, it was just on the tip of my tongue--ugg brain fart!
by SomethingAmiss February 4, 2015
An involuntary release of stupidity. Usually at the least opportune time.
Fred had a momentary brain fart and forgot that he left his term paper at home.
by Lalina October 12, 2009