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.
A spontaneous stupid (Stupid the noun, not stupid the adjective) usually accompanied by loss of train of thought and saying something fantastically stupid without realising it.
"Hey, what are you doing?"
"Hold secondary fire and the screen will change"
"What the hell?
"?? Oh, uhh... brainfart"
Blurb in your head outta nowhere, train of thought goes weird
Whoops sorry Brain Fart
A gap, interruption, or uncontrolled shift in a chain of thought resulting in a lull, pause, and/or blank stare during oral communication and sometimes involving the loss of short term memory.
Everyone at the meeting waited for Jim's response as he finally snapped out of his odd gaze into an unseen abyss. "Sorry", he said, "I just had a brainfart, what were we talking about?".
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!)
Adj. Used to describe a temporary loss of short-term memory.
I was about to answer her when I suddenly had a brainfart.
n. A massive, horrible release of stupid that is often offensive to the senses and may create a social faux pa in some settings. Brainfarts often result in an intense feeling of embarrassment and shame compounded by an inability to explain what the hell just happened.
I was supposed to call Roy Blount, Jr. for an interview at 10 a.m. PST, but I had a brainfart, forgot how to tell time, and managed to call him at 6:00 a.m. PST. I feel like an idiot.