Pronunciation: (i-fish'un-sē),[key] —n., —pl.-cies. 1. the state or quality of being efficient; competency in performance.
2. accomplishment of or ability to accomplish a job with a minimum expenditure of time and effort: The assembly line increased industry's efficiency. 3. the ratio of the work done or energy developed by a machine, engine, etc., to the energy supplied to it, usually expressed as a percentage.
4. See efficiency apartment.