Glossary Entry: Hitbox

Hitboxes are defined areas that can be used to detect collisions between objects. Most of the time, an object's hitbox will be slightly inside their sprite to allow for a little extra leeway, although it can be helpful for things like powerups to have a larger than normal hitbox.

Bullet Hell games are famous for making the player's hitbox as small as possible, allowing you to avoid anything that doesn't pass directly through the center of your character.