also: とんじゅ
noun
Honorific closing formula used at the end of formal letters, similar to 'Sincerely' or 'Respectfully yours'.
手紙の末尾に「頓首」と記す。
Write '頓首' at the end of the letter.
noun, noun or participle which takes 'suru'
Original meaning: a deep bow of respect, touching the head to the ground. Now rare as a standalone noun; the verb form 頓首する is occasionally used in historical or formal contexts.
昔の中国では、皇帝の前で頓首した。
In ancient China, people kowtowed before the emperor.