A circular saw.
circular saw definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
a saw in the form of a disk with a toothed edge, rotated at high speed as by a motor
circular saw definition by American Heritage Dictionary
A power saw for cutting wood or metal consisting of a toothed disk rotated at high speed. Also called buzz saw.