A joke, especially one which strikes the listener or reader as particularly humorous.(noun)
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Use "thigh-slapper" in a sentence
"I'll pause for a moment here while you recover from the gasping guffaws, the belly laughs that are no doubt incapacitating you right now as a consequence of that devastating thigh-slapper from Mayor Grose."
"Sarah Palin, Rudy Giuliani and much of the rest of the GOP apparently believe that small town mayoring is oh-so-important while community organizing is a real thigh-slapper."
"Trust me, readers of Thucydides would have found that last one a real thigh-slapper."