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.

Blurb in your head outta nowhere, train of thought goes weird

A sudden and involuntary (although depending on the source, not altogether unexpected) release of ignorance.

When someone does not perform an action that obviously should have been done, especially when you are under pressure and must think quickly.

The inability to remember something.

An involuntary release of stupidity. Usually at the least opportune time.

when you either blurt out something extremely wrong or embarassing infront of people or when you completely forget how to do something or say something