I'm pretty shocked there are people here who haven't heard anybody use the term salty before. It used to be a pretty popular term, but it's where you're from I guess.
Salty is a term used to describe somebody who either gets embarrassed, or does something to make themselves look stupid (like said above), or just has the worst luck in general and can never get a break. Like, for example if I was walkin and tripped on my shoe strings, you'd tell out 'salty'. If I tried to catch a ball coming towards me and it hit my face, you'd yell out 'salty'. Or if I died in my house and was found on the toilet, the cops would be thinking '...wow... The salt...'
-salty. I tried to describe that the best way I could.