To gormandize is to eat lots and lots of really tasty food. If your idea of a perfect night out is an enormous meal at a fancy restaurant, then you love to gormandize.
Although gormandize comes from the Middle French word gourmand, it's not related to the similar-looking gourmet. While a gourmet is someone who enjoys fine food, a person who tends to gormandize also loves delicious fare, but puts the emphasis on quantity. So a few bites of sashimi or foie gras might make you a gourmet, but eating them until you feel sick is gormandizing.