The Collaborative International Dictionary of English v.0.48:

Apologetic \A*pol`o*get"ic\, Apologetical \A*pol`o*get"ic*al\,
   a. [Gr. ?, fr. ? to speak in defense of; ? from + ? speech, ?
   to say, to speak. See Logic.]
   Defending by words or arguments; said or written in defense,
   or by way of apology; regretfully excusing; as, an apologetic
   essay. "To speak in a subdued and apologetic tone."
   --Macaulay.
   [1913 Webster]

WordNet (r) 3.0 (2006):

apologetic
    adj 1: offering or expressing apology; "an apologetic note"; "an
           apologetic manner" [syn: apologetic, excusatory]
           [ant: unapologetic]