Are there rats in this house? 쥐새끼 (jwisaekki) is a term literally meaning "offspring of a rat" can also be a derogatory term referring to a cunning person who is quick-witted in petty matters. Another thing is that 새끼 (saekki) is a common swear word ascribed to different people as a swear word, akin to bastard. Commonly appended to other animals increase the vitriolity (see 개새끼 (gaesaekki), "pup/baby dog" or a slang term for "son of a bitch"). Therefore, it could be said that Yukari could be refering to a "rat bastard" or "a fucking rat".