To ask someone to repeat something which needs clarification.
Jerry: She said there's some tractor story that she hasn't told me about.

George: Woah, back it up, back it up, Beep! Beep! Beep! Tractor story?

Jerry: Beep, beep, beep? What are you doing?
by Dick Armey October 20, 2006
Get the Back it up, BEEP! BEEP! BEEP! mug.