rocking shaft

Rock shaft \Rock" shaft`\ [Cf. Rock, v. i.] (Mach.) A shaft that oscillates on its journals, instead of revolving, -- usually carrying levers by means of which it receives and communicates reciprocating motion, as in the valve gear of some steam engines; -- called also rocker, rocking shaft, and way shaft. [1913 Webster]

Rocking \Rock"ing\, a. Having a swaying, rolling, or back-and-forth movement; used for rocking. [1913 Webster]