Geez, people Geardaddy gave the only right answer. A snap roll is simply a horizontal, one turn spin. Full up elevator, and full ailerons and rudder (in the same direction) are applied until the wing stalls. Some planes are hard to snap or won't snap at all. Trainers usually fall into this category.

If a plane loses too much airspeed, the wing will stop producing lift. Usually, it will fall off to one side or another. This is a stall which is usually followed by a snap roll/spin if correction isn't applied quickly.

A "snappy" plane is one which stalls easily and usually at a higher-than-expected airspeed. Aerobatic planes are often this type.

Dr.1