When looking for synonyms for the phrase "is on," there are several options to choose from. Some possible synonyms include "is active," "is underway," "is happening," "is occurring," "is taking place," and "is in progress." These phrases can be used to describe various types of events or situations, such as a sports game, a concert, a project, or a conversation. By using synonyms for "is on," you can add variety and depth to your language, making your writing or speech more interesting and engaging for your target audience.