Chronic \Chron"ic\, a. [L. chronicus, Gr. ? concerning time, from ? time: cf. F. chronique.]

1. Relating to time; according to time.

2. Continuing for a long time; lingering; habitual.

Chronic disease, one which is inveterate, of long continuance, or progresses slowly, in distinction from an acute disease, which speedly terminates.

Source: Webster's Revised Unabridged Dictionary (1913)