Rice stands for "Race Inspired Cosmetic Enhancements".
A ricer is someone who owns a car, usually with about 120hp, but thinks a body kit, rims, airplane wing, fart can, stickers, decals, ect will make the car fast because it will look fast. Ricers believe that adding tacky body mods will somehow get them pussy and give them 400hp to the wheels. Ricers are usually stuck-up white kids who fall for marketing schemes from magazines and "import performance" websites, mezmorized by the pictures of bodykits and big fart cans, and believing the "dyno proven 100hp gains" written in the product descriptions.
Ricer buys 120hp Civic because hes broke.
Ricer watches Fast and the Furious and wants 500hp to the wheels and some pussy.
Ricer buys an import magazine and sees a body kit that gains him 200hp "dyno proven".
Ricer buys the body kit but hes too lazy to paint it the color of his Civic, but he puts it on anyway.
Ricer revs his fart can at girls and they laugh.
Ricer trys to race a 350Z and loses the $500 bet because he did the "math" and thought he had 537hp and would win, i guess not.
Ricer hangs himself because he fails at life.