Google still has it documented on https://support.google.com/websearch/answer/2466433 and there is a none of these words option on https://www.google.com/advanced_search

Make sure you aren't putting the minus symbol in quotes. The quotes are what I see people get wrong. Many people still try to use the + symbol to indicate required but Google disabled that when working on Google+ and switched to quotes to indicate required words or phrases.