From the JargonFile:

'''grok'''
[from the novel ''StrangerInaStrangeLand,'' by RobertHeinlein, where it is a Martian word meaning literally "to drink" and metaphorically ''' "to be one with" '''] The emphatic form is GrokInFullness.
	* 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.
	* Used of programs, may connote merely sufficient understanding. "Almost all C compilers grok the 'void' type these days."
** False! There's a big difference between a C compiler that sort of more or less understands "void", and one that truly and completely groks it. But "void" is a relatively shallow subject, so it would be more to the point to say, e.g. "Wow, their C++ compiler groks the ISO standard on templates!"

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The current internet usage (July 2000) of ''to grok'' seems to me to be:

	* ''to understand, and assimilate successfully'' (for a human)
	* ''to accept and process successfully'' (for a program)

-- RogerBrowne