"Frothed the mouth" is a description commonly associated with anger, aggression, or insanity. There are a few different synonyms that can be used to convey this same idea. One option is "foamed at the mouth," which carries the same connotation of extreme emotion. Another possibility is "gnashed the teeth," which suggests a more physical manifestation of anger or frustration. Additionally, "raved" could be used to describe someone who is speaking quickly and intensely, potentially with a frothy mouth. Finally, "raged" or "seethed" both imply a level of anger and agitation that could lead to a frothy mouth.