Related Clues:

• Testify
• Stubborn sort
• Give one's word
• With 4-Down, upbraid in no uncertain terms
• Invoke misfortune
• Say '#@$%!'
• Scream ''#@$%!''
• Persistent bad luck
• Imprecation
• Turn blue?
• Use four-letter words
• Oath
• Declare flat out
• One that's ill-prepared?
• Turn the air blue