Related Clues:

• Super, slangily
• Like many a 21-Down
• Up on things, daddy-o
• Cool, as a daddy-o
• Cool, like a cat
• Sweet, slangily
• Hardly squaresville
• Excellent, in recent slang
• In the know, in old slang
• Lead-in for cat
• Great, in hip-hop slang
• In the know, daddy-o
• Not square, once
• "Cool," updated
• Excellent, in dated slang