The phrase "outer rim" refers to the outer edge or boundary of something, like a region or a circle. It signifies the farthest and often less-developed parts of a place or system. Full definition
Spray outer rim of crust with cooking spray; sprinkle crust with remaining 2 teaspoons sugar. (epicurious.com)
For the eyes, begin by lining inner and outer rim with eyeliner. (citystyleandliving.com)
Having said that, the metallic outer rim lends the handset a bit of flair and the hardware features are positioned logically — something that can't be said of all devices. (mobilesyrup.com)