The Collaborative International Dictionary of English v.0.48:

Chronic \Chron"ic\, a. [L. chronicus, Gr. ? concerning time,
   from ? time: cf. F. chronique.]
   1. Relating to time; according to time.
      [1913 Webster]

   2. Continuing for a long time; lingering; habitual.
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   Chronic disease, one which is inveterate, of long
      continuance, or progresses slowly, in distinction from an
      acute disease, which speedly terminates.
      [1913 Webster]