The Collaborative International Dictionary of English v.0.48:

Protractor \Pro*tract"or\, n.
   1. One who, or that which, protracts, or causes protraction.
      [1913 Webster]

   2. A mathematical instrument for laying down and measuring
      angles on paper, used in drawing or in plotting. It is of
      various forms, semicircular, rectangular, or circular.
      [1913 Webster]

   3. (Surg.) An instrument formerly used in extracting foreign
      or offensive matter from a wound.
      [1913 Webster]

   4. (Anat.) A muscle which extends an organ or part; --
      opposed to retractor.
      [1913 Webster]

   5. An adjustable pattern used by tailors. --Knight.
      [1913 Webster]

WordNet (r) 3.0 (2006):

protractor
    n 1: drafting instrument used to draw or measure angles

Moby Thesaurus II by Grady Ward, 1.0:

18 Moby Thesaurus words for "protractor":
   astrolabe, azimuth circle, azimuth compass, bevel,
   bevel protractor, bevel square, clinometer, goniometer,
   graphometer, pantometer, quadrant, radiogoniometer, sextant,
   theodolite, transit, transit circle, transit instrument,
   transit theodolite