A flag is a price chart pattern for technical analysis. A flag includes a strong price move (a nearly vertical line) that forms the flagpole, followed by an orderly and diagonally symmetrical pullback.
Flag can be bullish or bearish, and it occurs when there is a sharp price movement followed by a sideways price movement. This pattern ends when another sharp price movement heads in the same direction as the move that initiated the trend. Flag chart pattern is usually short lived, lasting generally between one and three weeks.