Definition 1 of 1
It means jumping in your gaddi, putting on Daler Mehendi/Mika/Gurdaas Maan at full blast on the sound system, and driving about aimlessly. Tremendous fun if done with the right company at the right time, and with enough money in your pocket to buy some good food - there's something about simbly driving around that makes you hungry after a while.
Avneet: "Haan yaar, same here. Chal, let's do some ghooming. I feel like having some nice tikka-shikka, we'll stop at that new tandoori joint on the way"