Person A - "Holy shit! You literally drug me through the parking lot last night."
Person B - "I thought you didn't remember anything from last night?"
Person A - "Blashback, Dude. Blashback."
Noun. Similar to a flashback, a blackback is the idea of finding out what actions you did the night before while blacked out. Usually found from pictures taken or people explaining your actions.
I had a blackback earlier. I saw a picture of myself in a fraternity house wearing a cat in the hat costume. Man, was I blacked out.