/grok/, /grohk/ (From the novel "Stranger in a Strange Land", by Robert A. Heinlein, where it is a Martian word meaning literally "to drink" and metaphorically "to be one with")
1. To understand, usually in a global sense. Connotes intimate and exhaustive knowledge.
Contrast zen, which is similar supernal understanding experienced as a single brief flash. See also glark.
2. Used of programs, may connote merely sufficient understanding. "Almost all C compilers grok the "void" type these days."