The Collaborative International Dictionary of English v.0.48:

Windpipe \Wind"pipe`\, n. (Anat.)
   The passage for the breath from the larynx to the lungs; the
   trachea; the weasand. See Illust. under Lung.
   [1913 Webster]

WordNet (r) 3.0 (2006):

windpipe
    n 1: membranous tube with cartilaginous rings that conveys
         inhaled air from the larynx to the bronchi [syn: trachea,
         windpipe]