Double lipped jumps are jumps with a rut near the top that creates a second lip to the jump face. Think of it as a jump with a single whoop on top.
It took a long time for me to figure out how to handle these. If you approach the jump normally, your rear wheel will buck like a horse and almost throw you off the bike. Inevitably you will nose dive. Proper suspension setup is key to these. If your suspension is iffy, you should do your best to avoid them at all costs or roll over them.
Anyway, you should approach these on the gas and have a majority of your body weight to the rear. My butt is basically on the rear fender. The front wheel usually handles it with ease. The rear wheel is the one you need to focus on. On the gas and weight towards the rear, the bike should skip over the second lip somewhat like a whoop and you'll sail to the landing of the jump.