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.

n. The act of wearing keys, colored handkerchiefs or other objects on the body to indicate sexual interests. Worn on left to indicate you're a bottom, on the right to indicate you're a top. There are several contradictory lists saying what each color code indicates. Mostly used in the gay male culture, and has branched out to lesbian and BDSM cultures, but may be dying out.
verb. to flag

To have sexual intercourse with a person from a sovereign nation, recognized by the United Nations, thus laying claim to that person’s “flag.”

To be a flagger. The act of flagging.
To say that you are going to do something and not do it. To get the reputation of being a flagger is not a good thing.

(v) The act of pulling another person's pants down.

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.

the act of taking any item into the restroom with you. i.e: book,laptop,phone,handheld game,Pokemon cards,food,dogs and cats,notebooks,briefcases.