Noun. Substance applied to food to increase spice, to make more intense. If describe as figuratively applying to an item, referenced item would increase in intensity, pace, speed or importance.

A hot girl in the drive thru or lobby at taco bell. Used as code so the female isn't aware that all the employees are staring at her.

The best and most highly regarded descriptor that one can use in reference to an object or event when evaluating said item's worth based on the Taco Bell Sauce Scale (or simply "Sauce Scale"). The term "Fire Sauce" is used to describe a girl that is banging, a badass object, delicious food, or an idea or event that is totally off the hook. Items that are declared as "Fire Sauce" are vastly more cool than items declared Mild Sauce, and slightly more B.A. than items declared Medium Sauce.

Fireball whiskey combined with applesauce