bare (one's) teeth
To display an angry, violent, or threatening reaction to or against something or someone, as does a dog or wolf when threatened. I will bare my teeth to anyone who tries to take away my land. We seemed to be getting along just fine, but she suddenly bared her teeth when I brought up religion. In my opinion, he's just very insecure and that's why he'll suddenly bare his teeth over some innocuous comment.
Farlex Dictionary of Idioms. © 2024 Farlex, Inc, all rights reserved.