Definitions of tart:

• noun:   pastry cup with a filling of fruit or custard and no top crust
• noun:   a small open pie with a fruit filling
• noun:   a woman who engages in sexual intercourse for money
• adjective:   harsh

  Example: "A tart remark"

• adjective:   tasting sour like a lemon
• name:  A surname (rare: 1 in 100000 families; popularity rank in the U.S.: #8021)