The Collaborative International Dictionary of English v.0.48:

Screw \Screw\ (skr[udd]), v. t. [imp. & p. p. Screwed
   (skr[udd]d); p. pr. & vb. n. Screwing.]
   1. To turn, as a screw; to apply a screw to; to press,
      fasten, or make firm, by means of a screw or screws; as,
      to screw a lock on a door; to screw a press.
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   2. To force; to squeeze; to press, as by screws.
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            But screw your courage to the sticking place,
            And we'll not fail.                   --Shak.
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   3. Hence: To practice extortion upon; to oppress by
      unreasonable or extortionate exactions.
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            Our country landlords, by unmeasurable screwing and
            racking their tenants, have already reduced the
            miserable people to a worse condition than the
            peasants in France.                   --swift.
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   4. To twist; to distort; as, to screw his visage.
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            He screwed his face into a hardened smile. --Dryden.
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   5. To examine rigidly, as a student; to subject to a severe
      examination. [Cant, American Colleges]
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   To screw out, to press out; to extort.

   To screw up,
      (a) to force; to bring by violent pressure. --Howell.
      (b) to damage by unskillful effort; to bungle; to botch;
          to mess up; as, he screwed up the contract
          negotiations, and we lost the deal.
      (c) [intrans.] to fail by unskillful effort, usually
          causing unpleasant consequences.

   To screw in, to force in by turning or twisting.

   Screw around,
      (a) to act aimlessly or unproductively.
      (b) to commit adultery; to be sexually promiscuous.

   Screw around with, to operate or make changes on (a machine
      or device) without expert knowledge; to fiddle with.
      [Colloq.] . -->
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The Collaborative International Dictionary of English v.0.48:

Screwing \Screw"ing\,
   a. & n. from Screw, v. t.
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   Screwing machine. See Screw machine, under Screw.
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WordNet (r) 3.0 (2006):

screwing
    n 1: slang for sexual intercourse [syn: fuck, fucking,
         screw, screwing, ass, nooky, nookie, piece of
         ass, piece of tail, roll in the hay, shag, shtup]