Related Clues:

• 'Can't be'
• Slangy turndown, and a hint to how 17-, 22-, 32-, 47- and 51-Across are formed
• ''I don't wanna''
• "Never mind"
• 'I doubt it, man'
• 'Nope ...'
• Grunting negative
• 'Prolly not'
• 'Aw, hell ___!'
• 'Not gonna happen'
• Casual "I'll pass"
• "Um, no thanks"
• Slangy "No way"
• ''I don't reckon so''
• Rural turndown