Source : Webster's Revised Unabridged Dictionary (1913)

Two-throw \Two"-throw`\, a. (Mach.)
   (a) Capable of being thrown or cranked in two directions,
       usually opposite to one another; as, a two-throw crank; a
       two-throw switch.
   (b) Having two crank set near together and opposite to one
       another; as, a two-throw crank shaft.