I think the term 'sexy' is just a personal opinion on everyone's part. It's like most describing definitions (ugly, beautiful, etc.) they are all just people's opinions on what they think fits that words. For me, when I think of sexy, I'd imagine it being some slender chick with nice long hair and a 'nice' body (as in, not too skinny, but not too heavy either) and as for a guy, maybe someone of average height with a 'nice' body as well (muscular, slightly tan, not too much body hair, etc) You know. Like, models. xD;
Well it certainly does not pertain to looks only, at least in my mind. Someone can be physically attractive but have the personality of a rock. I enjoy a little dose of intelligence and genuine kindness to be mixed in there.