barometer

Concise Oxford English Dictionary © 2008 Oxford University Press:
barometer/bəˈrɒmɪtə(r)/

▶noun

• 1 an instrument measuring atmospheric pressure, used especially in forecasting the weather and determining altitude.

• 2 an indicator of change: furniture is a barometer of changing tastes.

– derivatives
barometric adjective,
barometrical adjective,
barometry noun.