A bite or a nip?
It is not uncommon to hear than someone’s rabbit is biting. However, biting is a relatively uncommon behavior. What people perceive as bites are often just nips. A nip is like a pinch; a bite will draw blood, and rabbits have very different reasons for employing each behavior.
Nipping: Rabbits nip to get your attention; to tell you to move; to indicate annoyance. Nips can range from a very soft, almost nudge with their teeth to a good, hard pinch that may leave dents in your skin. Many rabbits are very gentle with their nips, though some can be a bit more enthusiastic.
The thing to remember is that if a rabbit nips you, they are NOT attacking you; they’re just communicating. If he’s nipping too hard, try a high squeal to let him know that it hurts. NEVER, EVER retaliate with physical contact such as hitting. Let him know verbally that he needs to be more gentle, and if you want more direct action, simply put him back in his pen and/or leave the room when he acts inappropriately. He’ll learn to change his behavior quickly.
Biting: Biting, on the other hand, is an act of aggression, usually when the rabbit is frightened and feels trapped. The rabbit may grunt, box or lunge at you before he bites, and he’ll probably draw blood.
If you have a biter, the first thing to do is assess what situations bring about this behavior. Is your rabbit scared of a specific person, object, item, smell, or behavior? Can this trigger be removed or changed? Can you coax your bunny into getting used to this frightening thing over time? Regardless, once you know why your rabbit is biting, you can at least be prepared to avoid that environment.
If your rabbit is so aggressive that you can’t overcome it, call one of the rescue groups noted on this site. They may be able to help.