Did you hear the word “busu（ブス）” somewhere?
In Japanese, “busu” means an ugly woman. It may also be used when cursing women. It is often expressed in katakana.
It is sometimes used for men, but it mainly refers to women. (For men, the words “gesu（ゲス）” and “buotoko（ブ男）” are used.)
Origin of “busu”
Originally, “busu” meant a crude drug that was taken from the aconite tuber or root and dried. The drug was mainly used as a cardiotonic and analgesic but contained highly toxic. Therefore, if you drunk without weakening it, your nerves will have been paralyzed.
It is said that for some reason the face when paralyzed by drinking the poison came to be called “busu”.
In recent years, the word “busu” has been used to refer to not only a person but also something of poor quality.
Also, recently, “busu” has been used in a positive sense combined with some words such as “busu kawaii（ブス可愛い）” meaning that it is ugly but cute.
Either way, it’s not a nice word to say, so hopefully, you only know the meaning and won’t use it.