a threaded fastener, either used with a nut or driven into a tapped hole, usually having a diameter of about 1/4 inch (6.4 mm) or less and a slotted head for tightening by a screwdriver.
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British Dictionary definitions for machine screw
a fastening screw with a machine-cut thread throughout the length of its shank
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