[ proh-trak-ter, pruh- ]

  1. a person or thing that protracts.

  2. (in surveying, mathematics, etc.) an instrument having a graduated arc for plotting or measuring angles.

  1. 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

Words Nearby protractor Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use protractor in a sentence

  • It contains a front pocket with an organizer for pens, pencils, and protractors, and its main compartment can hold textbooks and binders.

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

  • The student should have and use a protractor, such as is furnished with this book, for the numerous exercises which are to follow.

    A Text-Book of Astronomy | George C. Comstock
  • Rule another line along the same edge of the board as before and with a protractor measure the angle between these lines.

    A Text-Book of Astronomy | George C. Comstock
  • At that point find, by means of a protractor, the angle a projection of the chord makes with the face of the beam.

British Dictionary definitions for protractor


/ (prəˈtræktə) /

  1. an instrument for measuring or drawing angles on paper, usually a flat semicircular transparent plastic sheet graduated in degrees

  2. a person or thing that protracts

  1. a surgical instrument for removing a bullet from the body

  2. 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