Un-serviceable refers to something that is not functional or cannot be repaired. On the other hand, serviceable means something is functional and can be repaired. Some antonyms of un-serviceable can include functional, operative, useful, efficient, effective, and workable. These words emphasize the ability of something to operate correctly and provide the intended service. Another set of antonyms of un-serviceable includes dependable, reliable, sturdy, and durable. These words refer to something that is reliable and can perform its intended function for an extended period. In summary, the antonyms of un-serviceable depict a real item, which can work correctly and provide the required service.