Quite a puzzle

• Difficult question
• It's hard to answer
• Tough one
• It's not easy
• Gordian knot
• Baffled

Wiktionary Word definitions in Wiktionary
n. 1 One who stumps, or speaks, or orates, as a politician. 2 A difficult puzzle or problem. 3 (context archaic slang English) A boastful person.

WordNet Word definitions in WordNet
n. a particularly difficult or baffling question or problem [syn: poser , toughie , sticker ]

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Stumper \Stump"er\, n. One who stumps. A boastful person. [Slang] A puzzling or incredible story. [Slang, U.S.]