"Frothing at the mouth" is a colorful expression used to describe someone who is extremely angry or agitated. If you'd like to add some variety to your vocabulary, consider using some of these synonyms in place of the overused phrase: Fuming, seething, incensed, infuriated, steamed up, boiling, livid, enraged, irritated, maddened, worked up, beside oneself, raging, and ready to explode. All these words convey a sense of intense anger or agitation that could be used interchangeably with "frothing at the mouth." Varying your word choice will help you express yourself more creatively and effectively when describing someone who is struggling to contain their emotions.