Temperature is to isotherms as air pressure is to

In geography and meteorology, lines drawn on maps to connect points of equal value are called isolines. Each type of isoline has a specific name depending on the variable it represents.

Isotherms are lines connecting places with the same temperature. By the same logic, lines connecting places with the same atmospheric pressure are called isobars. The prefix iso- means "equal," and bar relates to pressure (from the Greek baros, meaning weight).

Isopleths is a general term for lines of equal value and does not specifically refer to pressure. Contours (contour lines) connect points of equal elevation above sea level. Isolines is likewise a generic umbrella term for all such lines. Only isobars specifically and exclusively denote lines of equal atmospheric pressure.

When you see an analogy question of this type, identify the specific isoline name that matches the variable: temperature pairs with isotherms, and air pressure pairs with isobars.