Definition of "Diet" :
noun: the act of restricting your food intake (or your intake of particular foods)
noun: the usual food and drink consumed by an organism (person or animal)
noun: a prescribed selection of foods
noun: a legislative assembly in certain countries (e.g., Japan)
verb: eat sparingly, for health reasons or to lose weight
verb: follow a regimen or a diet, as for health reasons
"He has high blood pressure and must stick to a low-salt diet."