Meaning of jackshaft

jack•shaft

Pronunciation: ( jak'shaft", -shäft"), [key]
— n. Mach.
  1. Also calleda 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.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.