A microburst is a damaging wind event resulting from a strong downdraft of downward-moving air current in a thunderstorm. As the downdraft hits the ground it spreads out along the ground and the damaging winds are produced. Affected outflow area of less than 2½ miles wide and peak winds lasting less than 5 minutes. Microbursts may induce dangerous horizontal/vertical wind shears, which can adversely affect aircraft performance and cause property damage.
Source: National Weather Service.