I occasionally use the term “elegant” in reference to design, generally meaning that complexity arises from the interaction of a few simple systems. The Civ V Krepost is one of my favorite examples, one bonus on one building creates three effects that yield Russia.
Definitions are as much about what is excluded as what is included, and our friend Wilhelm has effectively pointed to the opposite of elegance:
Paradox games are deep… as in fall in, founder, and quickly drown levels of deep. There are always lots of moving parts that influence each other that you have to keep track of so that the initial experience for all of there games seems to be getting totally lost in a morass of details thrown at you in rapid succession that quickly leads to overload, exiting the game, and rarely, if ever, returning to it.
This also highlights a reason why elegance in design is desirable. Elegance yields “easy to learn, hard to master.” Inelegance yield confusion and “eh, I’ll get back to it” … and not getting back to it. I never finished the tutorial for Banished because the first one involved multiple actions that each went several layers deep in menus, with little explanation of why would want to do those but a clear implication that these were basic actions that would frequently be necessary. User-oriented design: good interfaces naturally guide you to the action you want to take.