Related Clues:

• 'Nuts!'
• 'You gotta be kidding!'
• 'Horrors!'
• Emphatic denial
• 'Whoops!'
• 'Phooey!'
• 'Yikes!'
• 'Darn!'
• 'Yecch!'
• 'It can't be!'
• Cynic's retort
• See 50-Across
• 'Forget it!'
• 'Yuck!'
• Cry of despair