Most vexing is a phrase that refers to something that is extremely frustrating or annoying. There are several synonyms that can be used to convey the same meaning, including irksome, exasperating, maddening, bothersome, and aggravating. These words describe situations or circumstances that cause a person to feel irritated or aggravated, such as a tangled cord, a slow internet connection, or a difficult coworker. Other synonyms for most vexing include infuriating, troubling, and nettlesome. Regardless of the word used, the meaning remains the same: something is causing a significant amount of frustration or annoyance.