A bull market is a sustained period of rising prices across a market or a specific stock, typically accompanied by broad investor optimism and economic expansion. There's no single official trigger, but a common informal benchmark is a rise of 20% or more from a recent low, sustained over a meaningful period rather than a brief spike.
Bull markets vary widely in length — some have run for years — and don't move in a straight line; sharp short-term pullbacks can and do happen within a longer bull market without ending it. The term applies to individual stocks and sectors as well as to the market as a whole.
The name's origin is debated, but the common explanation ties it to how a bull attacks — thrusting its horns upward — as a visual mnemonic paired with the bear's downward swipe.