Short squeeze
A short squeeze is a fast price rise driven by short sellers being forced to buy back, because every short closes with a buy order.
Shorts often place their stops just above an obvious high. When price pokes above it, those stops trigger and buy, which pushes price into the next stops and liquidations, which buy again. The move speeds up because the shorts’ way out adds fuel to it.
Learn more: short selling explained and long and short positions.