Definition of wraparound
The term wraparound is mostly used in Omaha. When you have a good print in Omaha, it will be said that you have a wrap. But when you have a very strong draw that gives you more than 17 outs (an out is a card that can help our hand) we will say that you have a wraparound. For example, if you have 8s-9s-Kh-Qh on 2s-Ts-Jh, you have a wraparound. Here, all the spades will help you (you will have the flush), all 7s will give you a straight, and all aces will give you a straight. You also have a backdoor color draw with both hearts in your hands. The 8s will also give you a straight as well as the kings.
How to play your wraparound's?
If we take the example above, we don't have a pair, a straight or a flush, but with the number of outs we have, we will have to play our hand aggressively. By playing a wraparound aggressively, we maximize our fairness with our folding equity. If, for example, we make a check-raise on the higher flop, we encourage our opponent to fold. Every time he folds, he throws away the equity that is rightfully ours. And by playing aggressively a wraparound, we can induce our opponent to push all in on the flop with worse draws.