The phenomenon that occurs when a thunderstorm releases a powerful rush of wind and rain is a downburst. It begins as air descends rapidly from deep convection, then spreads outward in all directions when it hits the ground, producing damaging straight-line winds.
Rain can intensify the process in a wet downburst: falling precipitation adds drag, while evaporation and melting ice cool the surrounding air. The cooled air becomes denser and accelerates downward. A dry downburst can also occur when rain evaporates before reaching the surface, so little or no rain may be visible at ground level.
A microburst is a small-scale downburst, while a macroburst covers a larger area. Downbursts are often mistaken for tornadoes, but their wind spreads outward from an impact point instead of rotating inward around a central vortex. A derecho is a broader, long-lived windstorm that can contain multiple downbursts, not a synonym for one individual collapse.