or idler pulley
a loose pulley made to press or rest on a belt in order to tighten or guide it.
The Torturous Treadmill And Other Exercise Name OriginsLet's run down some of that hardware terminology and learn their interesting origin stories too!
Origin of idle pulley
First recorded in 1885–1890
Also called idle wheel.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for idle pulley
a freely rotating trolley used to control the tension or direction of a beltAlso called: idler
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