talking nonsense; describes someone who just say whatever that comes out of their mouth without giving any regards as to whether it is appropriate or whether it makes any sense or not [colloquial]
Examples (粵典–words.hk)
Cantonese
系又噏唔系又噏
係又噏唔係又噏
hai6 jau6 ap1 m4 hai6 jau6 ap1
to speak one's mind no matter whether one understands the subject