That's the dictionary definition, but that's only a weak shadow of it's true meaning. Coming out of the 1960s counter-culture, to grok something is to understand it completely, to live it, to grasp every bit of its possibilities.
That's what I've been doing for the last decade. Living the web, understanding it, working with its possibilities and learning its language. Including learning unusual words such as grok.
In 1991, when the Internet had just caught my interest, I posted a video as an experiment. The reaction showed me the power of the Internet, and literally changed everything for me.