Vindication, n.
Etymology: [L. vindicatio a laying claim, defense, vindication. See Vindicate.]
1. The act of vindicating, or the state of being vindicated; defense; justification against denial or censure; as, the vindication of opinions; his vindication is complete. Occasion for the vindication of this passage in my book. Locke.
2. (Civil Law)
The claiming a thing as one's own; the asserting of a right or title in, or to, a thing. Burrill.
Shades of meaning
Fernald has no entry of its own for vindication; he lists it under apology, defense.
Where he writes about it:
Plea ranges in sense from a prayer for favor or pardon to an attempt at full vindication. — from apology
Defense, exculpation, justification, and vindication are more properly antonyms than synonyms of apology in its modern sense, and should be so given, but for their connection with its historic usage. — from apology
Vindication is a triumphant defense of character and conduct against charges of error or wrong. — from defense