four-letter word
noun [ C ] uk/ˌfɔːlet.ə ˈwɜːd/ us/ˌfɔː.let̬.ɚ ˈwɝːd/
（四字母的）粗俗下流词，脏字
a short word that is considered to be extremely rude and offensive
Four-letter words are often edited out of films before they are shown on television. 电影在电视上放映之前，其中的脏字常常会被剪掉。