Duple

from WordNet (r) 3.0 (2006)

duple
    adj 1: consisting of or involving two parts or components
           usually in pairs; "an egg with a double yolk"; "a double
           (binary) star"; "double doors"; "dual controls for pilot
           and copilot"; "duple (or double) time consists of two (or
           a multiple of two) beats to a measure" [syn: {double},
           {dual}, {duple}]

from The Collaborative International Dictionary of English v.0.48

Duple \Du"ple\, a. [L. duplus. See {Double}.]
   Double.
   [1913 Webster]

   {Duple ratio} (Math.), that in which the antecedent term is
      double the consequent, as of 2 to 1, 8 to 4, etc.
      [1913 Webster]