The phrase "is with it" is an idiomatic expression that is often used to describe someone or something that is trendy, fashionable, or up-to-date. Antonyms for this phrase would include words such as outdated, obsolete, antiquated, or old-fashioned. These words imply that something or someone is no longer relevant or fashionable in contemporary society. Using these antonyms, we might describe something as being out of style or uncool. Alternatively, we might describe someone as being out of touch or behind the times. Overall, the antonyms for "is with it" convey a sense of being disconnected from current trends and societal norms.