A Buffet Intellectual is a less disparaging term than the more cynical pseudo intellectual, which has seen far more use than required. The term does not make any kicks about the actual intellectual's ability, but in the dilettante attitude of the individual. The random samplings of life that such a person goes through leaves him (or her) a veritable gold mine of random conversations but very little to seek them out for.
To identify a buffet intellectual is very easy - just start talking about something in the abstract and watch the classical allusions roll by. But the easiest way is, of course, to peek into the bookshelf. In the midst of all the professional books, you'll find books about Evolution and Dinosaurs. Or half a shelf of books about Quantum Physics and the Universe. Look more closely and you'll even find books about Economics and Social orders. Heck, you may even find a couple of books about Human Psychology.
A nibble here, a nibble there and not a mouthful anywhere. Such intellectual butterflys are curiousities who rarely achieve anything by such half-hearted dabbling. What is needed is focus and perseverance - not two days' worth of everything.