mouth off (about something)
phrasal verb with mouth verb [ T ] uk/maʊð/ us/maʊð/
UK informal disapproving
（在公开场合毫无顾忌地）发表意见，谈论
to express your opinions too loudly and publicly
I had to listen to Michael mouthing off about the government all through lunch. 整个午餐过程中我不得不听着迈克尔对政府大发议论。