apologetic

adj

1. Having the character of apology; regretfully excusing.

   “His tone was apologetic as he explained what had happened.”

   “Very different was he, however, from the brusque and masterful professor of common sense who had taken over the case so confidently at Upper Norwood. His expression was downcast, and his bearing meek and even apologetic.”

   “Aberdeen Joint is a fine station. Its approach is a real approach, not an apologetic side-street; its granite building has a dignity in keeping with the famous city skyline it faces, [...].”

   “At Paisley, a station staff member politely but firmly asks why RAIL is taking so many photographs. The reply - that it's a magnificent station worthy of pictures - changes his demeanour and he's then very apologetic and says he "has to ask".”

2. (dated)Defending by words or arguments; said or written in defense.

noun

1. (archaic, countable)A formal apology.
2. (countable, plural, uncountable, usually)A defensive method of argument.