The phrase "without rest" refers to performing an action or engaging in an activity without any interruption or break. To express this idea with different words, we can use synonyms such as continuously, nonstop, incessantly, tirelessly, unstoppably, unceasingly, relentlessly, persistently, and endlessly. These words suggest a perpetual state of motion or activity, and they highlight the absence of rest or pause. Whether we are talking about a person working without stopping, a machine functioning continuously, or a process that keeps going without interruption, these synonyms for "without rest" convey a sense of determination, energy, and unrelenting effort.