When you recline, you lounge or lean back. It isn't safe to recline while you're driving a car. However, it's perfectly safe to recline on your couch while you watch TV.
When you lie back in your hammock, you recline, and when you tilt your airplane seat into the lap of the person sitting behind you, you recline it. You might even have a special chair that reclines when you lean back in it, magically providing you with a footrest — it's called a recliner. Recline, from the Latin reclinare, "to bend back," shares a Proto-Indo-European root with lean.