A junkie term used to describe when you slowly pull on the plunger on the syringe, the blood will shoot into the syringe, having a flag waving appearance. This is a way of knowing that you've hit a vein.

remember kiddies, if it's red(dark red, vein) go ahead, if it's pink(bright red, artery) stop and think
Sarah knew she hit a vein when she saw the flag. She then pushed on the plunger to get the H in her system.
by tonitewedineinhell July 27, 2008
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When you're in a chess match, and you're running low on time so the opponent decides to insta-move or premove his pieces to time you out and win. Be faster and don't get flagged!!!
Anish Giri: has 5 seconds on the clock
Hikaru Nakamura: premoves the rest of the match
Anish: Not cool, Hikaru just flagged me!
Hikaru: There chat, I flagged him for content
by Zakhil the procrastinator April 6, 2021
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US Military terminology: the act of pointing the barrel of a firearm at another member of the US Military. Used especially during close-combat situations and during training.
During basic rifle marksmanship in basic training, a private got tackled for flagging a drill sergeant.

When clearing rooms, you must pay close attention to your muzzle so as to not flag your buddy.
by PFC King September 1, 2005
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A junkie term used to describe when the blood flings out into the syringe from pulling the plunger. This is a way of knowing you hit a vein. The reason it's called 'the flag' is because when the blood comes out it has a flag-waving appearance.
Sally knew she hit a vein when she saw the flag, she carefully pushed on the plunger of the syringe and waited anxiously for the rush.
by tonitewedineinhell July 11, 2008
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To start getting tired, lose energy or enthusiasm.
This could mean it's time for a coffee, red bull, power nap or swift exit.
"I'm starting to flag"
"He's really flagging now"
by Marshmallow girl February 5, 2010
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*TD on the 80 inch* THATS FLAGGGGGGGGGG
by THEONEANDONLYNBA May 19, 2022
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