Cal·i·pers n. pl.  An instrument, usually resembling a pair of dividers or compasses with curved legs, for measuring the diameter or thickness of bodies, as of work shaped in a lathe or planer, timber, masts, shot, etc.; or the bore of firearms, tubes, etc.; -- called also caliper compasses, or caliber compasses.
  Caliper square, a draughtsman's or mechanic's square, having a graduated bar and adjustable jaw or jaws. --Knight.
  Vernier calipers. See Vernier.
  ◄ ►
  Com·pass·es n., pl. An instrument for describing circles, measuring figures, etc., consisting of two, or (rarely) more, pointed branches, or legs, usually joined at the top by a rivet on which they move.
  Note: ☞ The compasses for drawing circles have adjustable pen points, pencil points, etc.; those used for measuring without adjustable points are generally called dividers. See Dividers.
  Bow compasses. See Bow-compass.
  Caliber compasses, Caliper compasses. See Calipers.
  Proportional, Triangular, etc., compasses. See under Proportional, etc.
  ◄ ►