noun
butterfly stroke
Swimming term; the stroke where both arms move simultaneously over the water.
彼はバタフライで100メートルを泳いだ。
He swam 100 meters using the butterfly stroke.
Refers to a very skimpy underwear or swimwear style; often used in fashion or adult contexts.
彼女はビーチでバタフライの水着を着ていた。
She was wearing a thong swimsuit at the beach.