Related Clues:

• Like all primes but one
• Other than what is implied
• Bartender's query
• Or --- (bully's words)
• Never used
• Lacking a match
• Atypical
• Something ___
• Quite unusual
• Unmatched, as socks
• Unfamiliar, as territory
• Opposite of 53-Down
• "So what --- is new?"
• Out of the ordinary
• Like Oscar and Felix's pairing