Related Clues:

• Locked, as a lavatory
• They're from Mars, in a book title
• Grown boys
• Chess or checkers pieces
• Occupied (5)
• Already occupied
• Adult males
• Knights, e.g.
• "Three __ and a Baby"
• Kasparov's sixteen
• Not vacant, as a restroom
• 'It's Raining ___'
• "So many __, so little time": Mae West
• Head word
• Queens, in chess