bosu
 n.— «Another innovation, this time from the United States, is Bosu—an acronym for “both sides up.” This is a giant inflatable exercise ball that is cut in half and which has replaced Step as the most sought after class type in American gyms.» —“Fitness meets fun in Italy” in Italy IOL (South Africa) May 27, 2005. (source: Double-Tongued Dictionary)

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