Ray Kurzweil defines it as the ability to use limited resources, including time, to achieve a set of goals (which may include survival, communication, solving problems, recognising patterns, performing skills). The products of intelligence may be clever, ingenious, insightful or elegant.

R. W. Young defines it as that faculty of mind by which order is perceived in a situation previously considered disordered.

To fairly adjudicate artificial intelligence the way you would adjudicate the skill of a magician. I maintain that how the result is achieved must be irrelevant. You must examine the intelligence in a black box. What we usually do is peek inside, and if we understand how the magic was achieved, suddenly decide that what we just saw was not real intelligence after all, just a cheap trick. I conjecture that all human intelligence is just a cheap trick. The reason we put it on such a pedestal is that we don’t understand all the tricks yet. We evolved these powers very quickly. They can’t be all that profound.