v. 1 To refresh yourself, like if you've been daydreaming during a meeting.
v. 2 To wake up.

Origin comes comes from the use of F5 as a "Refresh" key for MS Windows applications.
1.
Frank: Greg, what did you think of Tom's suggestion.
Greg: (Daydreaming) Huh? Wha?
Tom: F5, dude!

2.
I can't really F5 until my second cuppajava.
by Leif April 8, 2005
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Brock Lesnar hits Kurt Angle with the F5 and gets the pin to retain his WWE Undisputed Heavyweight Championship!
by SmackAhoe July 24, 2003
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a Tornado rated: (violent), with winds from 261-318 mph, causing (RARE) INCREDIBLE DAMAGE: Homes on slabs levelled with debris removed. Schools, motels and other marginally engineered buildings have considerable damage with exterior walls and roofs gone. Top stories demolished.
Holy fuck! That was a HUGE f5 tornado, moved my house 500 yards before crashing it in the middle of the highway... Totally demolished!
by Brian February 28, 2004
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The highest rating that can be applied to a Tornado, using the fujita scale.

F5 Tornados have wind speeds in the area of 261-318mph and do incredible amounts of damage.

Sometimes referred to as 'fingers of god'.
An F5 tornado hit Omaha on May 6, 1975......
by mrenigma August 2, 2004
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Reminding someone who you are or of something.
Boy 1: Ha your lame.

Boy 2: Yo do I have to F5 yo ass

Boy 1: No I was just kidding
by Darth Fader XII July 24, 2012
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I hit F5 to knock Craig off of inklink.
by Lo!s!er October 15, 2003
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(Frog Faction Female Frienship Fuckers)

Two chicks that fuck up there boyfriends friendships.
"Looks like we have another F5 comein along!"
by slbrey December 13, 2004
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