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²Today is considered—by some—the anniversary of the day the term cyberspace first saw print. Cyberspace, for those who have been playing Rip Van Winkle for 25 years, names "the online world of computer networks;" it refers especially to the Internet. As you might assume, cyberspace was coined by pairing the combining form cyber that means "computer; computer network" with the word space.

In the above sentence can you tell the meaning of "playing Rip Van Winkle"?
I know the man "Rip Van Winkle," who spend 20 years in one sleep, but "playing Rip Van Winkle" doesn't make any meaning to me.
Help me.
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It's just a humorous way to say "in case you have been disconnected from the world for a few decades and therefore don't know this."
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Grammar GeekIt's just a humorous way to say "in case you have been disconnected from the world for a few decades and therefore don't know this."

Indeed:
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The story of Rip Van Winkle is set in the years immediately before
(the early to mid-1770s) and after the American Revolutionary War (the
early to mid-1790s). Rip Van Winkle, a villager of Dutch descent,
lives in a nice village at the foot of New York's Catskill
Mountains. An amiable man whose home and farm suffer from his lazy
neglect, he is loved by all but his wife. One autumn day he escapes
his nagging wife by wandering up the mountains. After encountering
strangely dressed men, rumored to be the ghosts of Henry Hudson's
crew, who are playing nine-pins, and after drinking some of their
liquor, he settles down under a shady tree and falls asleep. He wakes
up twenty years later and returns to his village.
He finds out that
his wife is dead and his close friends have died in a war or gone
somewhere else. He immediately gets into trouble when he hails himself
a loyal subject of King George III, not knowing that in the meantime
the American Revolution has taken place. An old local recognizes him,
however, and Rip's now grown daughter eventually puts him up. As Rip
resumes his habit of idleness in the village, and his tale is solemnly
believed by the old Dutch settlers, certain hen-pecked husbands
especially wish they shared Rip's luck.

http://en.wikipedia.org/wiki/Rip_Van_Winkle
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Comments  
Just to add: Rip Van Winkle is a character in one of Washington Irving's stories.
 Marius Hancu's reply was promoted to an answer.
Students: We have free audio pronunciation exercises.
Thanks all of you. Thanks.