F5 is the function key to refresh a page on PC.

In Chinese/Japanese translation Web Novel and Light Novel communities, authors/translators will often have a regular time of the day that they'll upload the latest chapter. Practitioners of the F5 Sect have been known to repeatedly spam the F5 key near these times in the hope of being the first one to access the new chapter, and thus have the opportunity to make the first comment.

The 'Sect' is a joke referring to how many of the Chinese novels having martial practitioners belonging to various Sects (Clans, groups, etc.).

Therefore the users who single-mindedly hit the F5 key in pursuit of first comment ironically reflect the focus that'd be required of a martial cultivator in many of the novels that they are reading.
Lowlav (of Wuxiaworld forums):
F5 Sect is an organisation researching on the profound effects of throbbing F5, dealing with the order of rebirth. the pulse of internet. Cultivators of the laws of F5 are forever dominant in the comment sections all over the internet. It is a mystery with great power!

Ryuushima (Of Wuxiaworld forums):
They are a bunch of ---- that spam every chapter release with posts about being 1st , 2nd etc instead of talking about the actual chapter.

Minru (Of Wuxiaworld forums):
I refreshed the page and found a new skyfire chapter without a comment... instead of commenting first first first, i read the chapter. There still wasn't a comment so i nabbed first. Does this make ma F5 member because i got first or a F5 heretic because i read the chapter first?
by Deviant Antrax August 20, 2018
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A person who constantly refreshes their email inbox just in case someone has emailed them in the last 2 seconds
No matter how much of an F5 junkie you are, he's not going to email you!
by rob heeney March 11, 2004
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A tradition on the Roblox forums. As the forums have pathetic software, you can easily do this trick. You go to your/someones topic and hold F5, to make the post get alot of views. This is a form of trolling as popular posts get a star as an icon, which annoys other users on the forum.
Me: Let's F5Bomb some shit!

*Holds F5*

Me: Yay, i held F5!

Someone Else: FFFFUUUU ANOTHER TROLL F5 BOMBING EVERYTHING AARGH REPORT REPORT REPORT

Reporting is reporting someone who spams/posts adult content.
by WouterVL October 24, 2012
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When Reloading, Refreshing, To Refresh, Time of the month, So on so forth(hehe).
"This is taking to long, I'm F5-ing this shit!"
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To f5 something, is to exploit a weakness in a system that is so menial and stupidly pathetic, that the victim of the attick should be put in prison, as opposed to the perpetraitor.crashing hacking
Oh heh. I just F5'd babblers again.
by Miyabi July 11, 2003
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F5 Bombing is the act of holding down or rapidly pressing the F5 key in order to refresh the page, and therefore make the view count 'explode,' which is where the "bomb" part comes in.

Often used in forums where the threads have view count (such as 4Chan or Reddit, more commonly Roblox).

Used mostly by trolls, in order to make the view count seem substantially higher than it should be.

It's also a parody of the word F-bomb, which is basically the non-swear version of "fuck."
A: Hey dude, why does this thread have a lot of views compared to the other threads?
B: Someone must've F5 bombed this thread.
A: What a troll."
B: Same.
by KingKralj March 31, 2017
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People who nag constantly about the same issue, as if refreshing their questioneering forum entry ad infinitum.
'Hey John, do you want to see my holidays pics?' x40 in an hour.

'Good lord Dave, give it a rest. Getting real sick of your F5 Syndrome.'
by Onderkenkel April 17, 2014
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