To dabble is to do an activity without trying to be an expert or be excellent at it. You do the activity casually, not so seriously. You usually hear "dabble" with things like "dabble in witchcraft"...the person tries a little witchcraft, but isn't really serious about it. He has dabbled in investing, but he doesn't really know anything about it. People dabble in painting. (They aren't real artists. They just want to try it out.)

He has been known to dabble in learning a few languages.

I dabble in selling drugs. :P