A single-serving-size pie that can be either sweet or savory and usually is prepared without a top crust. The bottom crust can be made from either plain or rich pastry or from cookie and cracker crumbs. The term also refers to a full-size pie that is prepared in a special pan with straight side and a removable bottom. Tarts with sweet fillings are served as desserts, and savory tarts can be main dishes or appetizers. Tart also refers to a sharp or sour taste in foods.