someone who is not in a relationship, but is looking to meet new people to potentially have a relationship with. It is just a cliche' way of saying your single and looking.
it could actually mean both either a relationship or a hook up, it pretty much means that the person is single and okay with it and ready to get back out into the dating scene and see what may happen.. Now some people say this just when they want to have fun with other people or not really get serious because they are still a bit cautious of a full on relationship, but it is a good sign that the person is wanting to get back out there and start making new connections. if you like this person, go for asking if they want to hang out and see how it goes, you can normally tell from one date or hang out session if all they want is a hook up or a relationship. Good Luck!!
Ready to get out and start meeting people for friendship and possible relationship down the road, once you have gotten to know that person. It takes time to get to know someone and you must keep out the physical stuff as those have different emotions that get in the way of truly getting to know that person.