妄言多謝
also: ぼうげんたしゃ
Meanings
1
please excuse my reckless remarks; kindly forgive my thoughtless words
A formal, self-deprecating yojijukugo used deferentially in letters or speeches to apologize for one's own careless or arrogant statements.
Regarding my remarks the other day, I must apologize for my reckless words.
At the end of the letter, I wrote 'please excuse my thoughtless words.'