Webster's 1913 Dictionary
CALIPERS
Cal "i *pers, n. pl. Etym: [Corrupted from caliber. ]
Defn: 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.
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