What is the term for the quasi-horizontal flow of air resulting from a downburst?

The term for the quasi-horizontal flow of air resulting from a downburst is indeed known as an outburst. A downburst is a powerful and sudden downdraft that can occur during thunderstorms, causing a rapid descent of air to the ground. When this downdraft reaches the surface, it spreads out in a horizontal direction, creating strong, gusty winds. This phenomenon is characterized by its intense and localized nature, leading to airflow patterns that can significantly impact aircraft operations, particularly during takeoff and landing phases.

In contrast, the other terms refer to different wind conditions that do not specifically capture the essence of a downburst's horizontal air movement. A tailwind refers to a wind blowing in the same direction as the aircraft's flight path, enhancing its speed. A crosswind is wind that blows perpendicular to the aircraft's flight path, which presents challenges for maintaining control during landing or takeoff. A headwind refers to wind blowing directly opposite to the aircraft's direction, which can slow it down. None of these terms accurately describe the unique horizontal airflow created by a downburst.