Noun

1. A reference to any of several of the strongest English swearword that are also four letters long, especially those composing the so-called seven dirty words.
2. A swearword or any words considered to be taboo in a given scenario, (regardless of how many letters are actually in the word or words in question).

   To me, coming from you, 'Friend' is a four letter word. - Friend Is a Four-Letter Word, Cake