What Does it Mean if a Movie is "Flipped"?

I was on Youtube watching... well, I suppose I was listening to the
movie Friday the Thirteenth, and in the comment section people were
asking if the entire film was "flipped". What did they mean? Maybe
there was something special done to the movie - I wouldn't know. My
eyesight's not good enough to see those things.

Anyway, I'd appreciate it if someone could explain the term to me.
Thanks.