Back-breaking is an adjective that describes something that requires a lot of effort and is physically exhausting. There are many possible synonyms for this term, including arduous, laborious, strenuous, demanding, grueling, taxing, tiring, cumbersome, and onerous. Each of these words conveys a sense of hard work and physical exhaustion, but they may have slightly different connotations depending on the context. For example, arduous may suggest a long and difficult journey, while grueling may imply intense and prolonged exertion. Whether describing a difficult task, a challenging workout, or a heavy load to carry, these synonyms for back-breaking can help to vary your writing and add nuance to your descriptions.