It depends on the circumstance I would think. If it is just for a forum like this where you are just letting people know what you have some experience with it could just mean you know a little about the language.
But if it is for a online portfolio about yourself, or a resume, or anything relating to work experience I would only put the skills you know you are proficient in and could work with if you are asked to.
But seeing as you are mainly talking about the skill's option on this forum I would say list what you have some experience with (You don't have to be a expert).
a skill is an ability. Anyone can have skill or many skills. which is like saying anyone can have an ability or many ablilities. However, just because you can do something doesn't mean you can do it well. This is were mastering your skill comes from. What your talking about is mastering a skill itself.