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butterfly ballot

noun
  1. US a ballot paper in the form of two leaves extending from a central spine

Word Origin for butterfly ballot

C20: from its resemblance to a butterfly's wings
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012