I'm seeing the term y in a lot of ads. What is it short for?

so I'd suggest checking the urban dictionary.

No it usually appears to be part of a physical description-example "with a beautiful face and long, y legs that I can't wait to". At first I thought it was an acronym for young but it doesn't fit in many examples.

Maybe it is being used as a superlative as in definition number 9.

This seems to be the result of a robot removing the character sequence "s e x" wherever found in ads.  Girls often describe themselves as "s e x y" and get left with just "y".   You may notice some other beheaded word remains too; "a s s" gets removed, and probably some others.  

I've researched it out and it seems you're correct. Thanks to and everyone who took the time to answer

pretty sure its the same as saying V or join downtown, loads of peeps say "I went to dine at the Y" you know?

...Dine at the y wasn't his example and his example makes it clear this is something else.