was at a loss for words
私は言葉に窮した。
I was at a loss for words.
トムは言葉に窮した。
Tom was at a loss for words.
彼は言葉に窮した。
He was at a loss for words.
結婚してくれと言われたとき、私は言葉に窮した。
When I was asked to marry him, I was at a loss for words.