Noun: A two-door hatchback made by volkswagen noted as the "sport model" of the Golf line. GTi stands for "Grand Touring Injection", making light of the fuel injection system used on the first models in the 1970's. The GTi is the originator of the terms "Hot Hatch" and "Pocket Rocket", with many auto manufacturers following suit creating cheap knock-offs upon the GTI's arrival in the States in 1983. Always immitated, never duplicated. Known for crisp handling, brisk acceleration and quality material build, for relative low cost.
I kicked the snot out of some tool in a rice rocket with my trusty 1991 GTI with 175,000 miles. And it still looks sharp, too.
"Going through it" Generally describing the feeling one has during a night of extreme partying, almost always under the effects of some sort of party drug. Does NOT mean over dose, but sometimes the initial overwhelming feeling.