The Collaborative International Dictionary of English v.0.48:

Ductor \Duc"tor\, n. [L., fr. ducere to lead.]
   1. One who leads. [Obs.] --Sir T. Browne.
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   2. (Mach.) A contrivance for removing superfluous ink or
      coloring matter from a roller. See Doctor, 4. --Knight.
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   Ductor roller (Printing), the roller which conveys or
      supplies ink to another roller. --Knight.
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