noun
Technical term used in geography, cartography, and related fields to refer to lines on a map connecting points of equal elevation.
この地図の等高線は10メートル間隔で引かれている。
The contour lines on this map are drawn at 10-meter intervals.
等深線 refers to depth contours (isobaths) used in bathymetry, while 等高線 refers to elevation contours on land.
Compound of 等 (equal) + 高 (height) + 線 (line). The term is a direct calque of the English 'contour line'.