[jak-shaft, -shahft]
noun Machinery.
  1. Also called countershaft. a short shaft, connected by belting, gears, etc., that transmits motion from a motor or engine to a machine or machines being driven (distinguished from main shaft).
  2. a shaft on which an idle wheel or fairlead turns.

Origin of jackshaft

First recorded in 1895–1900; jack1 + shaft
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for jackshaft

Historical Examples of jackshaft

British Dictionary definitions for jackshaft


  1. a short length of shafting that transmits power from an engine or motor to a machine
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