noun \-ˈtrak-tər\

: a device that has the form of a half circle and that is used for drawing and measuring angles

Full Definition of PROTRACTOR

a :  one that protracts
b :  a muscle that extends a part
:  an instrument for laying down and measuring angles in drawing and plotting

First Known Use of PROTRACTOR

circa 1611


noun \-tər\   (Medical Dictionary)

Medical Definition of PROTRACTOR

: a muscle that extends a part—compare retractor b


noun    (Concise Encyclopedia)

Instrument for constructing and measuring plane angles. The simplest protractor is a semicircular disk marked in degrees from 0° to 180°. A more complex protractor, for plotting position on navigation charts, is called a three-arm protractor, or station pointer, and consists of a circular scale connected to three arms. The centre arm is fixed, while the outer two can be rotated to any desired angle relative to the centre one. A related instrument is the course protractor, which allows navigators to measure the angular distance between north and the course plotted on a navigation chart.


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