The Collaborative International Dictionary of English v.0.48:

Ply \Ply\, v. t. [imp. & p. p. Plied; p. pr. & vb. n.
   Plying.] [OE. plien, F. plier to fold, to bend, fr. L.
   plicare; akin to Gr. ?, G. flechten. Cf. Apply, Complex,
   Display, Duplicity, Employ, Exploit, Implicate,
   Plait, Pliant, Flax.]
   1. To bend. [Obs.]
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            As men may warm wax with handes plie. --Chaucer.
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   2. To lay on closely, or in folds; to work upon steadily, or
      with repeated acts; to press upon; to urge importunately;
      as, to ply one with questions, with solicitations, or with
      drink.
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            And plies him with redoubled strokes  --Dryden.
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            He plies the duke at morning and at night. --Shak.
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   3. To employ diligently; to use steadily.
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            Go ply thy needle; meddle not.        --Shak.
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   4. To practice or perform with diligence; to work at.
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            Their bloody task, unwearied, still they ply.
                                                  --Waller.
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