In Omaha, a wrap is a straight draw with more outs than an open-ended straight draw (OESD). In other words, wraps are straight draws where you have more than 8 outs. The most powerful wrap draw typically has 20 outs.
EXAMPLE “I was holding A-3-4-5, and the board came K-6-7. This is said to have a “wrap”, as any 3, 4, 5 or 8, would complete a straight.”
You have to be careful with wrap draws, however, since you can be chasing the sucker end of a straight, and there is the possibility that another player is flushing.
This video discusses a handy PLO wrap hand calculator for figuring out the outs you have and the nut outs.
This Pot Limit Omaha app (Omaha Wrap Wizard) can be downloaded for iPhone / iPad devices.