Tart = same as slapper, but harsher, suggesting they sleep around
However, the English language being what it is, it must not be confused with some other versions of tart 
Mince Tart.
Example: “I just baked a mince tart”
This does not mean I baked a minced slapper, to confuse the issue, this means fart.
To take the Majors’ approach
tart n. 1. A tart is much the same as a slapper, but is slightly less extreme and a little more omnisexual. Tarts spend hours perfecting make-up, hair, clothes, etc. before going out and waiting at the side of the dance floor to be pulled. Be warned, though - at the end of the evening, tarts tend to turn into slappers, just to make sure all that lip gloss doesn’t go to waste. Back, erm, on a more literary tack, the word may or may not be derived from “sweetheart”.
2. A small cake - perhaps a jam tart or a fruit tart. So when in “Alice Through the Looking Glass”, the rhyme goes “the knave of hearts, he stole the tarts” he wasn’t leaping off with his arms full of easy young ladies. We do also share the third meaning of the word, when it’s taken to mean “sour”.
Now we have many many members of TPR who could be compared to the “knave of hearts”, the one who always gets the tarts, onces again please do not confuse this into the knave eaten a can of beans 
Now going back to roots of what is the definition of a real “tart”. The term began life as a term used for advertisement cards left in telephone call boxes, specifically in London, Soho. These became known as “Tart-Cards”. So a tart believes they are gorgeous, and lets everyone know they think so by “advertising” the <cough> assets they have been blessed with. (naturally or surgically)
Then we have internet tarts…now the definition of this could lead to many a university thesis in years to come. In general terms, to know the real meaning, it helps if you have met Sgt Bilko :nod:
DT.