In networking, used to describe your exalted understanding of a particular network , typically by working on it for enough time to know all the areas of the network including memorising IP addresses, architecture, connectivity. As in, I grok my network.

Also used in reference to your experience of a technology, i.e. I know multicast but I don’t grok it.

As first used in the Heinlein novel Stranger in a Strange Land: Grok means to understand so thoroughly that the observer becomes a part of the observed—to merge, blend, intermarry, lose identity in group experience.

From the Jargon File – When you claim to ‘grok’ some knowledge or technique, you are asserting that you have not merely learned it in a detached instrumental way but that it has become part of you, part of your identity. For example, to say that you “know” LISP is simply to assert that you can code in it if necessary — but to say you “grok” LISP is to claim that you have deeply entered the world-view and spirit of the language, with the implication that it has transformed your view of programming. Contrast zen, which is a similar supernatural understanding experienced as a single brief flash.