To grok is to share the same reality or line of thinking with another physical or conceptual entity. Author Robert A. Heinlein coined the term in his best-selling 1961 book Stranger in a Strange Land. In Heinlein's view of quantum theory, grokking is the intermingling of intelligence that necessarily affects both the observer and the observed.
From the novel:
Grok means to understand so thoroughly that the observer becomes a part of the observed—to merge, blend, intermarry, lose identity in group experience. It means almost everything that we mean by religion, philosophy, and science—and it means as little to us (because of our Earthly assumptions) as color means to a blind man.
The Oxford English Dictionary defines grok as "to understand intuitively or by empathy; to establish rapport with" and "to empathize or communicate sympathetically (with); also, to experience enjoyment." Other forms of the word include "groks" (present third person singular), "grokked" (past participle) and "grokking" (present participle).
In an ideological context, a grokked concept becomes part of the person who contributes to its evolution by improving the doctrine, perpetuating the myth, espousing the belief, adding detail to the social plan, refining the idea or proofing the theory.
According to the book, drinking is a central focus on Mars where water is scarce. Martians use the merging of their bodies with water as a simple example or symbol of how two entities can combine to create a new reality greater than the sum of its parts. The water becomes part of the drinker, and the drinker part of the water. Both grok each other. Things that once had separate realities become entangled in the same experiences, goals, history, and purpose. Within the book, the statement of divine immanence verbalized between the main characters, "Thou Art God", is logically derived from the concept inherent in the term grok.
Heinlein describes Martian words as "guttural" and "jarring". Martian speech is described as sounding "like a bullfrog fighting a cat". Accordingly, grok is generally pronounced as a guttural "gr" terminated by a sharp "k" with very little or no vowel sound (a narrow IPA transcription might be [ɡɹ̩kʰ]).
Contemporary spiritual teacher Ram Dass, in Be Here Now, quotes a large passage from Stranger about the word.
According to Ed Sanders' book The Family, convicted murderer Charles Manson was a fan of Heinlein and Stranger and adopted many of the terms associated with both including "grok" and "thou art God".
The Jargon File, which describes itself as a "Hacker's Dictionary" and has thrice been published under that name, puts grok in a programming context:
The entry existed in the very earliest forms of the Jargon File, dating from the early 1980s. A typical tech usage from the Linux Bible, 2005 characterizes the Unix software development philosophy as "one that can make your life a lot simpler once you grok the idea".
Groklaw is a website with information on legal matters, usually of an IT nature.
GrokCode is a website covering computer programming and software development.
In a 1987 Life In Hell strip titled "What I Learned In School", a character representing "The Simpsons" creator Matt Groening is depicted being dressed down by an unseen "hip" college professor: "Mr. Gru-nink, I'm getting bad vibes from you. The rest of the class groks what is going on -- why can't you?"
Songwriter Stephin Merritt uses the word "grok" in the song "Swinging London", from the 1994 Magnetic Fields album "Holiday" - "you couldn't grok my race car but you dug the roadside blur".
Groks Science Show is a science radio show that uses the term in their name.
The name of a commercial federated search engine, grokker
In an episode of the television show "Silver Spoons" in 1985, Rickie calls chatting on a BBS "grokking".
In The Police song "Friends," lyrics state that the singer will "grok your essence."