Simulationist

A philosophy of game design that says you should be able to tell precisely what is going on in the gameworld. These are games that make you worry about lots of stuff, like where your characters will get their food, water, and medical supplies. They probably require every single action to have its own roll, so you have to roll to dodge instead of just giving your attacker a penalty to hit, because the game wants you to know whether he missed because he sucks or because you rock. They also give you a lot of options that you don't really need, like the ability to customize your characters down to the size and shape of their toenails. The math might not be very complicated, but there will be a lot of it.

Simulationist play is often contrasted with narrativist play, even though they're not really opposites. A simulationist game can include narrativist mechanics, and vice versa. Simulationism is kind of the opposite of freeform roleplay, where you're supposed to make shit up instead of following rules.