That is a rather impoverished explanation of a complicated word. A closer description would be "to understand something on such a deep and personal level that the lines of identity between it and you blur."
Here's a passage from the book that coined the term (as a word from an alien language)
> Grok means "to understand," of course, but Dr. Mahmoud, who might be termed the leading Terran expert on Martians, explains that it also means, "to drink" and "a hundred other English words, words which we think of as antithetical concepts. 'Grok' means all of these. It means 'fear,' it means 'love,' it means 'hate'—proper hate, for by the Martian 'map' you cannot hate anything unless you grok it, understand it so thoroughly that you merge with it and it merges with you—then you can hate it. By hating yourself. But this implies that you love it, too, and cherish it and would not have it otherwise. Then you can hate—and (I think) Martian hate is an emotion so black that the nearest human equivalent could only be called mild distaste.