The Collaborative International Dictionary of English v.0.48:

Effeminate \Ef*fem"i*nate\, v. t. [imp. & p. p. Effeminated;
   p. pr. & vb. n. Effeminating.]
   To make womanish; to make soft and delicate; to weaken.
   [1913 Webster]

         It will not corrupt or effeminate children's minds.
                                                  --Locke.
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The Collaborative International Dictionary of English v.0.48:

Effeminate \Ef*fem"i*nate\, v. i.
   To grow womanish or weak.
   [1913 Webster]

         In a slothful peace both courage will effeminate and
         manners corrupt.                         --Pope.
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The Collaborative International Dictionary of English v.0.48:

Effeminate \Ef*fem"i*nate\, a. [L. effeminatus, p. p. of
   effeminare to make a woman of; ex out + femina a woman. See
   Feminine, a.]
   1. Having some characteristic of a woman, as delicacy,
      luxuriousness, etc.; soft or delicate to an unmanly
      degree; womanish; weak.
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            The king, by his voluptuous life and mean marriage,
            became effeminate, and less sensible of honor.
                                                  --Bacon.
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            An effeminate and unmanly foppery.    --Bp. Hurd.
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   2. Womanlike; womanly; tender; -- in a good sense.
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            Gentle, kind, effeminate remorse.     --Shak.
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   Note: Effeminate and womanish are generally used in a
         reproachful sense; feminine and womanly, applied to
         women, are epithets of propriety or commendation.
         [1913 Webster]

WordNet (r) 3.0 (2006):

effeminate
    adj 1: having unsuitable feminine qualities [syn: effeminate,
           emasculate, epicene, cissy, sissified,
           sissyish, sissy]

Moby Thesaurus II by Grady Ward, 1.0:

60 Moby Thesaurus words for "effeminate":
   AC-DC, amphierotic, autoerotic, bent, bisexed, bisexual, breakable,
   brittle, butch, campy, cheap-jack, chicken, cobwebby, crumbly,
   dainty, delicate, delicately weak, deviant, flimsy, fragile, frail,
   frangible, gay, gimcrack, gimcracky, gossamery, homoerotic,
   homosexual, jerry, jerry-built, lesbian, light, lightweight,
   mannish, muliebrous, namby-pamby, old-womanish, papery,
   pasteboardy, perverted, prissy, puny, queer, sapphic, shattery,
   sissified, sissy, sissyish, sleazy, slight, soft, tacky,
   transvestite, tribadistic, unmanly, unsubstantial, weak, wispy,
   womanish, womanly