That feeling after taking your girlfriend out to a nice restaurant, the kind that leaves both your stomach and wallet empty, in order to please her enough to get laid that night.
Can also apply to any situation where the restaurant just doesn't serve a proportionate amount of food for the price.
The phrase stems from rushing out to get Taco Bell after the aforementioned situations in order to satisfy that hunger known in Taco Bell lingo as "The Fourth Meal." Comes from the Taco Bell commercials where, after emerging from triumphantly satisfying his stomach, the man yells, "I'M FULL!!!"
Man, I just took my girlfriend out to a Japanese restaurant, where I paid 30 bucks and only got one measly roll of sushi. I'm gonna need Taco Bell after this.
...granted, I'm still gonna get laid tonight.