An explanation or excuse: an account given to justify or clarify one's actions or to respond to criticism.
彼は遅刻した理由を弁明したが、納得できる説明ではなかった。
He offered an explanation for being late, but it was not convincing.
会社の不祥事について、社長が弁明の会見を行った。
The president held a press conference to explain (or defend) himself regarding the company's misconduct.
弁明の余地がなく謝罪するしかない。
There is no room for excuses; all we can do is apologize.