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[proh-trak-ter, pruh-] /proʊˈtræk tər, prə-/
a person or thing that protracts.
(in surveying, mathematics, etc.) an instrument having a graduated arc for plotting or measuring angles.
Anatomy. a muscle that causes a part to protrude.
Origin of protractor
From Medieval Latin, dating back to 1605-15; See origin at protract, -tor Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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Examples from the Web for protractor
Historical Examples
  • The protractor has a graduated disk, and is adjustable so it can be disposed at any angle.

  • He was using a protractor, which was divided into Galactic degrees.

    The Players Everett B. Cole
  • protractor: that which extends or lengthens out: applied to muscles.

  • We'll start with the one with the coconut ice and the protractor, please.

    The Judge

    Rebecca West
  • At that point find, by means of a protractor, the angle a projection of the chord makes with the face of the beam.

  • Then, if we have a protractor, we may apply it to the lines and see how many degrees of angle they contain.

  • The pupil who cannot see the equality of vertical angles intuitively better than by the use of the protractor is abnormal.

    The Teaching of Geometry David Eugene Smith
  • It is also fairly accurate to run a line at any angle to a given line by sighting along two pins stuck in a protractor.

    The Teaching of Geometry David Eugene Smith
  • Measure the angle CAX, either in degrees, with a protractor, or by sighting along a piece of paper and marking down the angle.

    The Teaching of Geometry David Eugene Smith
  • In the absence of any outdoor work a protractor may be used to measure the exterior angles of a polygon drawn on paper.

    The Teaching of Geometry David Eugene Smith
British Dictionary definitions for protractor


an instrument for measuring or drawing angles on paper, usually a flat semicircular transparent plastic sheet graduated in degrees
a person or thing that protracts
a surgical instrument for removing a bullet from the body
(anatomy) a former term for extensor
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for protractor

1610s, "one who lengthens (an action)," from Medieval Latin protractor, agent noun from Latin protrahere "to draw forward" (see protraction); sense of "instrument for drawing angles" first recorded 1650s.

Online Etymology Dictionary, © 2010 Douglas Harper
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protractor in Medicine

protractor pro·trac·tor (prō-trāk'tər, prə-)
A muscle that extends a limb or other part.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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