Related Clues:

• Cancel omnibus without anyone initially on board?
• Unfasten, loosen
• Invalidate, like a marriage
• Loosen, as a tie
• Computer user's lifesaver, often
• Word-processing reversal
• Computer function often represented by a counterclockwise arrow
• Repeal, rescind
• Icon with a curved arrow
• Wreck party after upsetting Greek character
• Declare null
• Go back, on a PC
• Render null
• "Go back," on a PC
• Ruin a Continental celebration