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general::
Phrase(s): show one’s teeth [and] bare one’s teeth
Fig. to act in an angry or threatening manner. (Alludes to what an angry wolf or dog does.) • We thought Bob was meek and mild, but he really showed his teeth when Jack insulted his girlfriend. • The enemy forces didn’t expect the country they invaded to bare its teeth.
McGrawhill's American Idioms And Phrasal Verbs