grok \GRAWK\ (transitive verb slang) - To understand, especially in a profound and intimate way. Slang.
'"Even if you explain it in short words I'm not going to grok it, okay?" Benjamin frowned the uncomprehending frown of someone whose learning of the English language had missed the word "grok" entirely."' - Eric Flint, Andrew Dennis, '1634: The Galileo Affair"
The slang word grok was coined by Robert A. Heinlein in the science fiction novel "Stranger in a Strange Land", where it is a Martian word meaning literally "to drink" and metaphorically "to be one with". It was adopted into the vocabulary of 1960's youth and hackish jargon, whence it has become a part of net culture.