Can you tell us where you have seen the term "good efficiency?" That is not a term used that I know of. You are undoubtedly referring to efficiency, of which there are MANY different forms and measures of efficiency. If you can, please provide a bit more information on what it is you are looking at.
I would say efficiency is quite simply the ratio of useful "stuff" over the total amount " stuff" available. For example a light bulb has x amount of energy (electrical) available. It uses y amount of energy to produce light, therefore the efficiency is x/y x 100%. Good efficiency is about improving this ratio towards 100% Edit: Silly me, it should be y/x * 100%
Here ya go Fred: http://www.cnet.com/5208-6033-0-10.html?forumID=105&threadID=104376&messageID=1195130&start=-1 Honda Civic hybrid? Not very good efficiency!
I have never heard of "good efficiency" as a technical term. There is just efficiency, which is readily 'quantifiable'. However, there can be efficiencies of components or systems, and one can talk of 'net' or 'gross' depending on what is incorporated in the formula for efficiency. "Good efficiency" sounds like a subjective term, where 'good' is simply an adjective. Then there is the matter of 'reliability' or 'availability'.