Related Clues:

• Negative function word
• National Do __ Call Registry
• Yup's opposite
• ''No way''
• With 40-Across, later
• Naysayer's word
• 'Nuh-uh'
• -- -for-profit
• "Not likely"
• "It's __ for Me to Say": Mathis hit
• ''Ripley's Believe It or ___!''
• 'Unh-unh!'
• "Only kidding!"
• "Au contraire!"
• "Forget it"