Fetching details from the dictionary...

to be stumped; to be at a loss; to be at one's wits' end; to be nonplussed
to be fed up; to be tired (of); to be unable to bear; to be annoyed
会議での彼の終わりのない長話に全員が閉口してしまった。
I was overwhelmed by his long story.
暑さに閉口しながら仕事を続けた。
I continued working despite being overwhelmed by the heat.
顧客からの度重なる無理な要求に担当者は閉口している。
I'm at a loss with the repeated requests.