There are several synonyms for the phrase "beside oneself" that can be used to convey a similar meaning. Some options include "out of control," "furious," "livid," "irritated," "enraged," and "in a rage." Each of these synonyms implies a state of extreme emotion or agitation, indicating that someone is deeply upset or disturbed by something that has happened. Whether it's anger, frustration, or another powerful emotion, using synonyms for "beside oneself" can help to portray the intensity of the situation and the impact it has had on the person experiencing it.