expression, godan verb (-ru)
be at a loss for words; be stuck for words
Used when someone cannot find the right words to say, often due to emotion, surprise, or difficulty expressing oneself.
突然の質問に、彼は言葉に詰まった。
He was at a loss for words at the sudden question.
感謝の気
I tried to express my gratitude, but I got stuck for words.