Plain English Meaning

A pressure-measuring device that uses small sealed metal cans to sense changes in air pressure. The cans squeeze or swell as the surrounding pressure changes, and that tiny movement is shown on a dial.

Full Definition

An instrument that measures atmospheric pressure using one or more sealed metal capsules (aneroid wafers) that have had most of the air removed from them. As outside air pressure changes, the capsules expand or contract, and that mechanical movement is linked to a pointer or other indicator to show the current pressure.

Context Anchor

Seen in altimeter discussions, especially when explaining how an aircraft altimeter turns air pressure changes into an altitude indication.

Derivation

From the Greek 'a-' meaning 'without' and 'neros' meaning 'liquid' — literally 'without liquid.' The name distinguishes it from older barometers, which used a column of liquid mercury. An aneroid barometer does the same job using sealed metal capsules instead of liquid.