Real Dictionary

Mercator projection in American English
a conformal projection on which any rhumb line is represented as a straight line, used chiefly in navigation, though the scale varies with latitude and areal size and the shapes of large areas are greatly distorted
a method of making maps in which the earth's surface is shown with the meridians as parallel straight lines spaced at equal intervals and the parallels of latitude as parallel straight lines intersecting the meridians at right angles but spaced farther ap

Mercator projection in British English
noun: an orthomorphic map projection on which parallels and meridians form a rectangular grid, scale being exaggerated with increasing distance from the equator