The Collaborative International Dictionary of English v.0.48:

Poncho \Pon"cho\, n.; pl. Ponchos. [Sp.]
   1. A kind of cloak worn by the Spanish Americans, having the
      form of a blanket, with a slit in the middle for the head
      to pass through. A kind of poncho made of rubber or
      painted cloth is used by the mounted troops in the United
      States service.
      [1913 Webster]

   2. A trade name for camlets, or stout worsteds.
      [1913 Webster]

WordNet (r) 3.0 (2006):

poncho
    n 1: a blanket-like cloak with a hole in the center for the head