Merriam-Webster Collegiate Dictionary - tart

 I. adjective  Etymology: Middle English, from Old English teart sharp, severe; akin to Middle High German traz spite  Date: before 12th century  1. agreeably sharp or acid to the taste a ~ apple  2. marked by a biting, acrimonious, or cutting quality a ~ rejoinder  • ~ish adjective  • ~ly adverb  • ~ness noun  II. noun  Etymology: Middle English ~e, from Anglo-French  Date: 14th century  1. a dish baked in a pastry shell ; pie: as  a. a small pie or pastry shell without a top containing jelly, custard, or fruit  b. a small pie made of pastry folded over a filling  2. earlier slang, girlfriend, probably short for jam ~, rhyming slang for sweetheart prostitute