a wind that blows steadily toward the equator from the northeast in the tropics north of the equator and from the southeast in the tropics south of the equator
See trade wind in American Heritage Dictionary 4
(wĭnd)
noun
Any of a consistent system of prevailing winds occupying most of the tropics, constituting the major component of the general circulation of the atmosphere, and blowing northeasterly in the Northern Hemisphere and southeasterly in the Southern Hemisphere. Often used in the plural.