Backwards. Upper teeth are supposed to slightly overlap lower teeth. If upper jaw is too small, or lower jaw is too large, or teeth are malposed some or all of your upper teeth may fall inside your lower teeth. That's a cross bite. If you have a cross bite, please consult with a qualified orthodontic specialist. Ask your general dentist for a referral.
Crossbite. A crossbite usually means that, when you bite your teeth together, your lower front teeth close in front of your upper front teeth, or your lower back teeth close to the outside of your upper back teeth.