Link motion /(lĭṉk" mō"shŭn)/

Link· mo·tion

Link motion

n.
  1. A valve gear, consisting of two eccentrics with their rods, giving motion to a slide valve by an adjustable connecting bar, called the link, in such a way that the motion of the engine can be reversed, or the cut-off varied, at will; -- used very generally in locomotives and marine engines. (Steam Engine)