Fainting or writhing in agony; to be overcome by intense pain. Also used figuratively for being overwhelmed by strong sensations (e.g., extreme emotion, embarrassment).
激しい腹痛で悶絶し、救急車で運ばれた。
He writhed in agony from severe abdominal pain and was taken away by ambulance.
彼のギャグにみんなが悶絶して笑いが止まらなかった（冗談めかして）。
Everyone was 'in stitches' at his joke and couldn't stop laughing (figurative/humorous use).
唐辛子を食べて悶絶しそうになった。
I almost writhed in agony after eating the chili pepper.