A person who has a Japanese car that was made to go fast and handle well (Skyline, S2000, Impreza, RX7, even the Miata), and makes it go faster and handle better without making it look ugly is not a ricer.
A person who has a Japanese(typically, though ricers have been known to rice-out American and European cars) car (like the Civic) that was made to go slow, and makes the car look incredibly ugly by way of "aero kits" that are ineffective/detrimental to the car's aerodynamics is a ricer. This person could also have installed an "exhaust system" which eliminates all backpressure, including the backpressure the engine needs, which causes backfiring, loss of torque, and the infamous "farting in a coffee can" exhaust note. Furthermore, this person could have installed a set of comically large rims wrapped with almost non-existent tires, eliminating all sidewall and imparting to the car the ride qualities of a broken suspension. Lowering could have been performed by cutting the springs, which reduces ride height by softening the springs, which in turn renders the springs less useless. This is why ricers must slow to 2 miles per hour for speedbumps to avoid bottoming out.
The true hallmark of a ricer is that little to no useful engine modifications have been performed.
A non-ricer may have a small spoiler for rear downforce to even out weight distribution and increase stability at speed.
A ricer has so much "aero kits" that there is drag slowing the car, or the downforce that kicks in at speed will not let the car accelerate.