The hour, usually between 8:30 and 9:30PM, when more of your friends are signed onto Facebook than usual.
Person 1: Hey. It's Facebook hour and 49 of my friends are signed onto Facebook!
by gamerdude949 May 27, 2009
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While a regular hour has sixty minutes, a Facebook-hour is usually shorter; due to the unnecessary amount of time spent on Facebook when one should be doing other activities.

It can vary from fifty minutes, all the way down to just fifteen minutes left on an hour.
Mark: Why did it take you five hours to do your math homework yesterday?

Tim: It took two and a half, actually, but was on Facebook half the time

Mark: Oh, so five Facebook hours?

Tim: Yes
by Norway90 March 7, 2011
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The hours of the night that begin somewhere around 11:30 PM and extend until mid-morning, when society frowns on interrupting a friend's late-night stalking or lurking on Facebook. Facebook feels quiet as a library, and you feel as though you are the only one on the entire site, because by this time your Live Feed has slowed to a halt. It is customary to ignore the presence of other online facebookers at this time unless they are very close friends, to allow everyone ample time for mindless late night facebooking, which may include but it not limited to Farmville, Mass Picture Stalking, or wall-to-wall reading.
Person 1: "Dude, last night I had 36 friends online, but I couldn't talk to them because it was during Facebook Quiet Hours."

Person 2: "Sucks. Same thing happened to me."
by GingerSnapRayRay May 15, 2010
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1.The time of day when your list of friends on chat exceeds from one friend online to forty friends online.

2.The time of day when everyone is logged into facebook. Usually between 4:00-5:00
Man 1: Dude, I was on facebook yesterday at 4:30, there were so many people on my facebook chat broke.

Man 2: It must have been Facebook Rush Hour.
by Phil Muhweenuh April 15, 2010
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