We often get questions about slang words listeners see in the newspaper or (more likely) hear in movies, TV programs, and songs. The problem with slang is that it keeps changing. Words that were slang five years ago may no longer be used. Slang tends to be very short-term, although some expressions do have a longer life.
In general, I don’t recommend second language speakers use slang words, especially “new” slang, unless they really understand how it should be used and in what contexts. This is often difficult for a non-native to figure out. It is best, in most cases, just to speak in “normal” English, and avoid using slang that you don’t completely understand.
One place to look for definitions of slang is the Urban Dictionary. This is a Wikipedia-type of website, where readers submit definitions and sample sentences. This is a good place for slang that comes from recent songs or movies.
Note: There is also a lot of vulgar or “bad words” on the website, so use it carefully. Also, remember that because this is a site where anyone can submit definitions, not all of the definitions are correct. Look for words/phrases that have at least five or ten definitions to make sure you are getting the right idea. And don’t think that because it appears in Urban Dictionary, it is a common phrase. Most of these words are not common – again, look for words that have lots of definitions to get an idea of just how common it is (or Google the word or phrase and see how many websites have it).