A supercell is a severe thunderstorm with a deep rotating updraft.
Supercell thunderstorms are the largest, most severe class of single-cell thunderstorms.
It has been argued that there are really only two types of thunderstorms: supercell and ordinary, though some have four classifications: single-cell, multi-cell, squall line, and supercell.
Supercells are usually found isolated from other thunderstorms, although they can sometimes be embedded in a squall line.
Because they can last for hours, they are known as quasi-steady-state storms.