The Collaborative International Dictionary of English v.0.48:

Hectic \Hec"tic\, a. [F. hectique, Gr. ? habitual, consumptive,
   fr. ? habit, a habit of body or mind, fr. ? to have; akin to
   Skr. sah to overpower, endure; cf. AS. sige, sigor, victory,
   G. sieg, Goth. sigis. Cf. Scheme.]
   1. Habitual; constitutional; pertaining especially to slow
      waste of animal tissue, as in consumption; as, a hectic
      type in disease; a hectic flush.
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   2. In a hectic condition; having hectic fever; consumptive;
      as, a hectic patient.
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   Hectic fever (Med.), a fever of irritation and debility,
      occurring usually at a advanced stage of exhausting
      disease, as a in pulmonary consumption.
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The Collaborative International Dictionary of English v.0.48:

Hectic \Hec"tic\, n.
   1. (Med.) Hectic fever.
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   2. A hectic flush.
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            It is no living hue, but a strange hectic. --Byron.
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WordNet (r) 3.0 (2006):

hectic
    adj 1: marked by intense agitation or emotion; "worked at a
           feverish pace" [syn: feverish, hectic]