Definitions for "Macroburst"
Subject: The Earth A strong downdraft (downburst) greater than 4 km wide that can occur beneath thunderstorms. A downburst less than 4 km across is called a microburst.[ Pics List
A larger downburst affecting an area greater than 2.5 km in diameter.
A downburst affecting an area greater than 4 kilometres across and having damaging winds. Macrobursts are generally longer-lived than the smaller microbursts. Macrobursts have been documented to 'wrap-up' into weak tornadoes, however these would be classified as gustnadoes as they are not directly associated with storm-scale rotation. See also microburst.