Arc discharge is a term used to describe an electric discharge that takes place in low-pressure gas or vacuum environment, producing a bright arc, often accompanied by a crackling sound. The phenomenon is commonly observed in welding, lighting, and electrical engineering. Some excellent synonyms for arc discharge include electric arc, arc flash, arc lamp, spark discharge, plasma discharge, and electric spark. These synonyms could be useful for writers in technical fields or anyone working with electrical equipment. It's important to use the appropriate synonym depending on the context to ensure a clear and accurate description of the phenomenon.