The antonyms for "nonoperational" are operative, functional, active, operational, going, working and functional. If something is nonoperational, it basically means it is not working, not functioning or not in operation. In contrast, if something is operative or functional, it means it is working perfectly fine and running smoothly. Similarly, if something is active and operational, it is in motion and currently functioning. Being operational and going means that it is in motion and is currently in use. Above all, when something is considered to be functional, it implies that it is dependable, reliable and efficient.