[mahy-kruh-burst] 
| an intense, localized downdraft of air that spreads on the ground, causing rapid changes in wind direction and speed; a localized downburst. |
| mi·cro·burst (mī'krō-bûrst') n. A sudden, violent downdraft of air over a small area. Microbursts are difficult to detect and predict with standard weather instruments and are especially hazardous to airplanes during landing or takeoff. |
microburst
pattern of intense winds that descends from rain clouds, hits the ground, and fans out horizontally. Microbursts are short-lived, usually lasting from about 5 to 15 minutes, and they are relatively compact, usually affecting an area of 1 to 3 km (about 0.5 to 2 miles) in diameter. They are often but not always associated with thunderstorms or strong rains. By causing a sudden change in wind direction or speed-a condition known as wind shear-microbursts create a particular hazard for airplanes at takeoff and landing because the pilot is confronted with a rapid and unexpected shift from headwind to tailwind.
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krəˌbɜrst