Sometimes the dictionary definition isn't enough to understand the meaning of a word in a new context. "Hacker", up to about a decade ago, certainly meant "an expert at solving problems with a computer", but that meaning is not what people are referring to now. The dictionary hasn't caught up with modern parlance yet. Today's meaning is more along the lines of "A person whose expertise in a subject allows them to do things in new and innovative ways." To be described as a "<something> hacker" is a compliment.