The term Arcade shooter refers to a shooter game which has unrealistic elements that are in place to enhance a players enjoyment. It is contrasted by the realistic tactical shooter.
An arcade shooter can contain several of the following:
A magic satchel in which players can store a very large number of weapons and items
A quantifiable percentage of health, usually with no ill-effects on performance from massive wounds
The ability for the player to shrug off weak attacks like bullets with minimal health loss