Antonyms for "being seated" would be "standing", "walking", "running", "jumping" or "lying down". When a person is standing, their weight is supported by their feet rather than by a chair or other furniture. Walking or running involves moving around while on one's feet. Jumping involves briefly leaving the ground to propel oneself forward. Lying down involves reclining or resting on a surface, such as a bed or couch. All of these actions are opposite to "being seated", which implies a person is sitting on a chair or surface for an extended period of time.