The Collaborative International Dictionary of English v.0.48:
Direct-acting \Di*rect"-act`ing\, a. (Mach.)
Acting directly, as one part upon another, without the
intervention of other working parts.
Direct-acting steam engine, one in which motion is
transmitted to the crank without the intervention of a
beam or lever; -- also called direct-action steam
Direct-acting steam pump, one in which the steam piston rod
is directly connected with the pump rod; -- also called
direct-action steam pump.