Esp. of a machine: working, running; functional, operative; proceeding vigorously. Also: (of a fire) well alight, vigorously burning.

Able to fulfil a specific function or perform a designated role; working or operative.

In a condition of readiness to perform some intended (originally military) function; able and ready to function. Also in weakened sense: working…

colloquial (originally U.S.). Chiefly in predicative use. Functioning properly; ready and prepared; fulfilling all conditions necessary to proceed.