whilst climbing, this is the act of throwing a leg to a certain position that gives you more balance or allows you to reach an otherwise unreachable hold.
By flagging his right leg, Tristan was able to reach the final hold on the route.
In the game type Capture the Flag, the act of moving towards your own base as fast as possible, usually involving ignoring enemies on the way, thus putting yourself at risk. First used by the Call of Duty 2 and 4 clan, 1337.
Zach: Woah! How did you score the flag so quickly?
Derek: I pulled out my pistol, ignored all the enemies, and started flagging back to our base.