Definition of tarts:
(n) :
A type of small open pie, or piece of pastry, now typically containing jelly (US) / jam (UK) or conserve, or sometimes other fillings (chocolate, custard, egg, butter, historically even meat or other savory fillings).
(adj) :
Sharp to the taste; acid; sour.
(adj) :
(of wine) High or too high in acidity.
(adj) :
(figuratively) Sharp; keen; severe.
(n) :
(British, slang) A prostitute.
(n) :
(slang, derogatory, by extension) Any woman with loose sexual morals.