The Collaborative International Dictionary of English v.0.48:

Waistcloth \Waist"cloth\, n.
   1. A cloth or wrapper worn about the waist; by extension,
      such a garment worn about the hips and passing between the
      thighs.
      [1913 Webster]

   2. (Naut.) A covering of canvas or tarpaulin for the
      hammocks, stowed on the nettings, between the quarterdeck
      and the forecastle.
      [1913 Webster]

WordNet (r) 3.0 (2006):

waistcloth
    n 1: a band of material around the waist that strengthens a
         skirt or trousers [syn: girdle, cincture, sash,
         waistband, waistcloth]