expression
A formal, self-deprecating apology meaning 'I have no excuse' or 'I am terribly sorry'. Used when one feels deep regret and acknowledges fault.
ご迷惑をおかけして、申し訳が立ちません。
I am terribly sorry for causing you trouble.
こんな結果になってしまい、申し訳が立たない気持ちです。
I feel inexcusable for this outcome.
From 申し訳 (excuse, apology) + が + 立たない (does not stand), literally 'an excuse does not stand', meaning one cannot justify one's actions.