The Collaborative International Dictionary of English v.0.48:

Duck \Duck\, v. t. [imp. & p. p. Ducked; p. pr. & vb. n.
   Ducking.] [OE. duken, douken, to dive; akin to D. duiken,
   OHG. t?hhan, MHG. tucken, t["u]cken, t?chen, G. tuchen. Cf.
   5th Duck.]
   1. To thrust or plunge under water or other liquid and
      suddenly withdraw.
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            Adams, after ducking the squire twice or thrice,
            leaped out of the tub.                --Fielding.
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   2. To plunge the head of under water, immediately withdrawing
      it; as, duck the boy.
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   3. To bow; to bob down; to move quickly with a downward
      motion. " Will duck his head aside." --Swift.
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