intransitive. To perform one's function; to operate, function. Also: to officiate at a function.
intransitive. To fulfil one's function; to work, to operate.
intransitive. Of a furnace, boiler, oven, etc.: to begin or continue to burn fuel, to come or be alight; to be in operation. Cf. sense 6.
intransitive. To be in action, to be functioning. Cf. sense 6.