The term "un-burdensome" means something that is not cumbersome or heavy to carry. Its antonyms could be "cumbersome," "oppressive," "onerous," "troublesome," or "burdensome." Cumbersome refers to something that is physically large, unwieldy, and difficult to manage or carry around. Oppressive is something that weighs heavily on the mind, body, or spirit, causing distress or anxiety. Onerous denotes a task or responsibility that is difficult to bear or execute. Troublesome means something that is causing irritation or annoyance. And, burdensome is a term that is closely related to un-burdensome, but conveys the opposite meaning - indicating something that is hard to bear, oppressive, or harsh.