When you get so wasted/faded that your brain stops storing conscious memory's, and anything that you do while blacked out will not be remembered tomorrow.
"blacking out is the action that leads to being blacked out."
Black outs can be very unsettling/dangerous, but also create potentially hilarious situations.
"Dude, Bob's blacking out."
"Why? What's he on?"
"He took a couple Ambiens and another three shots."
when one consumes so much of a substance (typically alcohol) that one cannot remember one's actions at a later time, be it later in the night or the morning after