The Collaborative International Dictionary of English v.0.48:

Tango \Tan"go\ (t[a^][ng]"g[=o]; Sp. t[aum][ng]"g[=o]), n.; pl.
   Tangos (-g[=o]z). [Sp., a certain dance.]
      (a) A difficult dance in two-four time characterized by
          graceful posturing, frequent pointing positions, and a
          great variety of steps, including the cross step and
          turning steps. The dance is of Spanish origin, and is
          believed to have been in its original form a part of
          the fandango.
      (b) Any of various popular forms derived from this.
      (c) a musical tune appropriate for this dance.
          [Webster 1913 Suppl. +PJC]