The Collaborative International Dictionary of English v.0.48:

Head gear \Head" gear`\, or Headgear \Head"gear`\
   (h[e^]d"g[=e]r`), n.
   1. Headdress.
      [1913 Webster]

   2. Apparatus above ground at the mouth of a mine or deep
      well.
      [1913 Webster]

WordNet (r) 3.0 (2006):

headgear
    n 1: clothing for the head [syn: headdress, headgear]
    2: the hoist at the pithead of a mine
    3: stable gear consisting of any part of a harness that fits
       about the horse's head

Moby Thesaurus II by Grady Ward, 1.0:

60 Moby Thesaurus words for "headgear":
   back band, backstrap, bearing rein, bellyband, bit, blinders,
   blinds, breeching, bridle, cap, caparison, cavesson, chapeau,
   checkrein, cheekpiece, chinband, cinch, collar, coverchief,
   crownband, crupper, curb, gag swivel, girth, hackamore, halter,
   hames, hametugs, handkerchief, harness, hat, headcloth, headdress,
   headpiece, headstall, headtire, headwear, hip straps, jaquima,
   jerk line, kerchief, lid, lines, martingale, millinery, noseband,
   pole strap, reins, ribbons, saddle, shaft tug, side check, snaffle,
   surcingle, tack, tackle, trappings, tug, winker braces, yoke