When an organization or community is doing poorly enough that its smartest people, seeing the writing on the wall, leave for better opportunities elsewhere. This is common in business and other organizations that perpetuate a common goal or mission and once purged it typically accelerates the demise of the organiztion.

For example: Facebook's poor stock performance since it's IPO and lack of favorable stock options for employees puts them at risk of brain drain. Many will likely head over to Google or Apple, but they'll be in trouble.
Mark Zuckerberg: Sheryl, can find me those repots on Zynga's...Hey?! Why are wearing a Google sweatshirt?!

Sheryl Sandberg: Sorry Mark. We had a good run, but your lack of focus on ad revenue and overvalued IPO has caused this drop in FB stock value with no end in sight. I and the others are leaving before the stock tanks.

Mark Z: The others? They're all leaving Facebook? You can't! We'll never survive this brain drain!

Sheryl: Yeah, sorry. You should've thought about that before going public.
by Tenacious Faulker August 3, 2012
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An unfortunate and potentially traumatic experience which occurs when a heterosexual male is masturbating to a porno flick, and notices that the porno flick is about to enter the money shot scene. The masturbator furiously races to match the timing of his ejaculation with that of the porn star's facial spray onto the cum-craving whore. However, just when the masturbator is about to climax, the scene inexplicably cuts from the gaping whore to a close-up of the porn star's sweaty face as he is jizzing. As a result, the masturbator ends up draining his willy to the porn star rather than the cum slut, leading to a deeply unpleasurable orgasm, severe long-term emotional stress, and a dark era in the masturbator's existence as he questions the meaning and purpose of life. The porn star's face is generally accented by a visible vein popping from his beefy forehead, hence the term Vein Drain.
Dude, I was jerking off to "Butt Fuck Sluts Go Nuts Pt. 9" last night, but just as I was about to erupt in sludge, the camera cut to the roid-head, leading me to vein drain. I have decided to leave all my belongings to you in my will.
by Joey the Grip June 20, 2009
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"Dude, I need to drain the lizard"...

Ten minutes later

"Dude, look at this.. I'm draining the lizard"
by HumanMetronome November 27, 2013
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A female who is on this planet to only receive the cock. She takes so much cock that her holes are just drains for sperm.
"Mary has fucked the whole team in the office"
"Really, that whore is a complete fucking sperm drain"
by MickyHow July 21, 2013
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A pretty good song by Nirvana. This was Kurt's favorite song that he wrote. His second favorite is Pennyroyal Tea.
Chew your meat for you
pass it back and forth
in a passionate kiss
from my mouth to yours
I Like you
by York April 20, 2004
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Drain Tactics is a type of tactic that can be used in pretty much every day to day activity, The art of a Drain tactic is to find a quicker and more often than not a dodgey/Bad way of doing things.
If a "Drain Tactic Is performed, the person on the other side of the tactic will usually get Drained because of the poor quality. See Drained or Drainer

"Drain Tactics" Are to be used by people who have no care or pride in what they are doing, whether it be their full time job or just baking a cake.
The Quality of a job performed using "Drain tactics" is noticeably different to the way it should be done.
Jaso: Dad Why did the kitchen fall apart?
Dad: Because the dickhead must have had somewhere to go and used drain tactics to get it installed as quick as he could.

Hannah: Tayla how did u get here so fast?,

Tayla: Used Drain Tactics on all the intersections, i cut off and drained that many people its not even funny. See Drained or Drainer

Josh: Steve uses Drain Tactics to win matches.
by Str8rippinpro June 14, 2010
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