The term "be labor" can be replaced with numerous synonyms, such as "overexert", "strain", "toil", "exhaust", "sweat", "overwork", "struggle", "persevere", "grind", "labor", and "tire". These words all pertain to working too hard or too long, and causing physical or mental exhaustion. "Be labor" implies an individual is working diligently to complete a task, but these synonyms provide varying levels of intensity to describe how much effort and energy are being exerted. Depending on the context, one of these synonyms can replace "be labor" to provide a more specific meaning or tone to the sentence or phrase.