Is it still slang?

I’ve been finding a fair number words that seem to be slang but are often tech/geek oriented. Sometimes I just have to wonder what they are because I don’t know of a way to look them up — web searches are very hit and miss for this sort of thing. For example, what is a Wiki? But if a book has already been written about the word, can it still be slang? Or it just another area of technology that I never happened to encounter?