Similar to a flashback or flashforward but shows events that would transpire if a
character's life would have turned out differently than what happened in the original timeline.
This concept was
first started in the 6th season of the tv series
Lost.
Guy1: "
Man, imagine what my life would be
like in a flashsideways timeline if Emily didn't break up with me?"
Guy2: "I know
man, I know. Just let the tears out!"