The Collaborative International Dictionary of English v.0.48:

Waistband \Waist"band\, n.
   1. The band which encompasses the waist; esp., one on the
      upper part of breeches, trousers, pantaloons, skirts, or
      the like.
      [1913 Webster]

   2. A sash worn by women around the waist. [R.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

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

Moby Thesaurus II by Grady Ward, 1.0:

22 Moby Thesaurus words for "waistband":
   baldric, band, bandolier, bellyband, belt, breechclout, cestus,
   cincture, cummerbund, dhoti, diaper, fascia, girdle, girt, girth,
   loincloth, loinguard, moocha, napkins, sash, waist belt,
   waistcloth