What is the scariest war the world has ever known?
세상에서 제일 무서운 전쟁이뭔지 알아요?
Get it? 무섭다 is the base form of the word for "scary" or "scared". As it is a "ㅂ" verb, it is irregular when conjugated, dropping the ㅂ and adding the 워. This is the 반말 (ban-mal, informal) conjugation of the verb, to say it formally, you would need to simply add 요: 무서워요.
Now, why is this funny? It's a play on the pronunciation of the word "war" in English. "워" sounds like "war" to Korean speakers (and maybe to Bostonians who like to drop their "r"s at the end of words, too). I hope you like this joke, and try it on your friends today!
When the syllable block preceding the ㅂ in irregular ㅂ verbs has an ㅏ or ㅗ the ㅂ is dropped and a 와 is added. ex. 돕다 (to help) --> 도와요
When the syllable block preceding the ㅂ in irregular ㅂ verbs has any other vowel, the ㅂ is dropped and a 워 is added. ex 무섭다 (scary) --> 무서워요
Conjugate the following three irregular ㅂ verbs.
징그럽다 (gross/ disgusting)
Do you know another irregular ㅂverb? Post it in the comments with a conjugation and a translation!
*check your answer in the comments*