a. [ L. rota a wheel. See Roll, v., and cf. barouche, Rodomontade, Roué, Round, a., Rowel. ] Turning, as a wheel on its axis; pertaining to, or resembling, the motion of a wheel on its axis; rotatory; as, rotary motion. [ 1913 Webster ]

Rotary engine, steam engine in which the continuous rotation of the shaft is produced by the direct action of the steam upon rotating devices which serve as pistons, instead of being derived from a reciprocating motion, as in the ordinary engine; a steam turbine; -- called also rotatory engine. --
Rotary pump, a pump in which the fluid is impelled by rotating devices which take the place of reciprocating buckets or pistons. --
Rotary shears, shears, as for cloth, metal, etc., in which revolving sharp-edged or sharp-cornered wheels do the cutting. --
Rotary valve, a valve acting by continuous or partial rotation, as in the four-way cock. [ 1913 Webster ]