|a.||1.||Causing effects; producing results; that makes the effect to be what it is; actively operative; not inactive, slack, or incapable; characterized by energetic and useful activity; as, an efficient officer, power.|
|n.||1.||An efficient cause; a prime mover.|
|Adj.||1.||efficient - being effective without wasting time or effort or expense; "an efficient production manager"; "efficient engines save gas"|
inefficient - not producing desired results; wasteful; "an inefficient campaign against drugs"; "outdated and inefficient design and methods"
|2.||efficient - able to accomplish a purpose; functioning effectively; "people who will do nothing unless they get something out of it for themselves are often highly effective persons..."-G.B.Shaw; "effective personnel"; "an efficient secretary"; "the efficient cause of the revolution"|