protractor

Plural: protractors

Noun

• drafting instrument used to draw or measure angles
• One who, or that which, protracts, or causes protraction.
• A circular or semicircular tool for drawing or measuring angles.
• An instrument formerly used in extracting foreign or offensive matter from a wound.
• A muscle that extends an organ or part; opposed to retractor.
• An adjustable pattern used by tailors.

Synonyms

semicircle