Indicated altitude is defined as:

Indicated altitude refers specifically to the height above sea level that is displayed on the altimeter when it is set to the standard pressure setting (29.92 inHg) at sea level or the local altimeter setting adjusted for the aircraft's location. When a pilot sets the altimeter correctly, it reads the atmospheric pressure at the given altitude, allowing the pilot to determine the aircraft's altitude above sea level accurately.

This means that indicated altitude can fluctuate if the altimeter is not set to the correct pressure for the location or if the barometric pressure changes due to weather conditions. It is important to always check and adjust the altimeter setting to ensure safety and accurate altitude readings during flight operations.