The terms zonal and meridional are used to describe directions on a globe. Zonal means "along a latitude circle" or "in the west-east direction"; while meridional means "along a meridian" or "in the north-south direction".
These terms are often used in the atmospheric and earth sciences to describe global phenomena, such as "meridional wind flow", or "zonal temperature". (Strictly speaking, zonal means more than simply a direction as it also implies a degree of localization in the meridional direction, so that that the phenomenon in question is localized to a zone of the planet.)
For vector fields (such as wind speed), the zonal component (or x-coordinate) is denoted as u, while the meridional component (or y-coordinate) is denoted as v.
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