The Collaborative International Dictionary of English v.0.48:

Sickly \Sick"ly\, adv.
   In a sick manner or condition; ill.
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         My people sickly [with ill will] beareth our marriage.
                                                  --Chaucer.
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The Collaborative International Dictionary of English v.0.48:

Sickly \Sick"ly\, v. t.
   To make sick or sickly; -- with over, and probably only in
   the past participle. [R.]
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         Sicklied o'er with the pale cast of thought. --Shak.
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         Sentiments sicklied over . . . with that cloying
         heaviness into which unvaried sweetness is too apt to
         subside.                                 --Jeffrey.
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The Collaborative International Dictionary of English v.0.48:

Sickly \Sick"ly\, a. [Compar. Sicklier; superl. Sickliest.]
   1. Somewhat sick; disposed to illness; attended with disease;
      as, a sickly body.
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            This physic but prolongs thy sickly days. --Shak.
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   2. Producing, or tending to, disease; as, a sickly autumn; a
      sickly climate. --Cowper.
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   3. Appearing as if sick; weak; languid; pale.
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            The moon grows sickly at the sight of day. --Dryden.
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            Nor torrid summer's sickly smile.     --Keble.
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   4. Tending to produce nausea; sickening; as, a sickly smell;
      sickly sentimentality.
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   Syn: Diseased; ailing; infirm; weakly; unhealthy; healthless;
        weak; feeble; languid; faint.
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WordNet (r) 3.0 (2006):

sickly
    adj 1: unhealthy looking [syn: sallow, sickly]
    2: somewhat ill or prone to illness; "my poor ailing
       grandmother"; "feeling a bit indisposed today"; "you look a
       little peaked"; "feeling poorly"; "a sickly child"; "is
       unwell and can't come to work" [syn: ailing, indisposed,
       peaked(p), poorly(p), sickly, unwell, under the
       weather, seedy]