GGB It is the discipline of treating the menu as a financial document — classifying every item by how often it sells (its sales mix) and how much cash margin it contributes per plate, then deciding deliberately what to promote, reprice, reposition or remove. The aim is a menu that steers customers toward the dishes that actually make money, rather than one that simply lists what the kitchen can cook.
From Menu Engineering: How to Price a Restaurant Menu for Profit — the full reading, with the method behind this answer.