give someone a piece of your mind
give (someone) a piece of (one's) mind
To tell someone how one feels, often while expressing anger or frustration. I had to give Sarah a piece of my mind after she left my car a mess for the third time this week. Boy, the boss really gave me a piece of his mind after that awful meeting.
give someone a piece of your mindINFORMAL
If you give someone a piece of your mind, you speak angrily to them because they have done something to annoy you. You can't let people get away with behaviour like that. You should have given her a piece of your mind! If I'd been the parent, I'd have given the teacher a piece of my mind.