Related Clues:

• Brief turndown
• Pig Latin refusal
• "Dream on!"
• 'Can't be'
• Slangy turndown, and a hint to how 17-, 22-, 32-, 47- and 51-Across are formed
• 'Yep' opposite
• "Not possible"
• 'Ain't happening'
• ''I don't wanna''
• "Never mind"
• Yup's antonym
• 'I doubt it, man'
• 'Nope ...'
• Grunting negative
• 'Prolly not'