belly flop noun 3verb 3forms 4 noun3 •A style of diving into a body of water in which the surface impact is made mostly by one's abdomen. •A similar move performed on a trampoline. •(slang) A flop; an utter failure. verb3 •To perform this type of dive. •To perform this type of trampolining move. •(slang) To flop; to be an utter failure.The director's first three movies belly flopped. formsbelly flopped · belly flopping · belly flops · belly-flops