What does grok mean?

Grok is a slang verb sometimes used by geeks roughly meaning "to understand completely" or more formally intuitive understanding

The term originated in Robert Heinlein's novel Stranger in a Strange Land, where it is used by a man raised with Martians and literally means "to drink".

A character in the novel (not the primary user) defines it:

"'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 we are from Earth) as color means to a blind man."

Now you now.