Source : Webster's Revised Unabridged Dictionary (1913)

Holdfast \Hold"fast`\, n.
   1. Something used to secure and hold in place something else,
      as a long fiat-headed nail, a catch a hook, a clinch, a
      clamp, etc.; hence, a support. ``His holdfast was gone.''
      --Bp. Montagu.

   2. (Bot.) A conical or branching body, by which a seaweed is
      attached to its support, and differing from a root in that
      it is not specially absorbent of moisture.

Source : WordNet®

holdfast
     n : restraint that attaches to something or holds something in
         place [syn: {fastener}, {fastening}, {fixing}]