1. One of a handful of words with four letters that are considered profanity. Jimmy was suspended from school after the teacher heard him shout a number of four-letter words at his classmates. The move received its rating solely due to its high amount of four-letter words.

2. By extension, a word that has a positive or neutral connotation but that is treated as if it were highly negative. Such words do not have to literally contain four letters. Young people today seem to think "school" is a four-letter word. All they want to do is sit around and play video games all day. To most voters, "taxes" is a four-letter word.