Definition
An altitude in the atmosphere where the air pressure equals a specific value. Because atmospheric pressure decreases with height, every pressure value corresponds to a particular height above the ground at any given moment. Altimeters work by sensing pressure and converting it into an indication of altitude based on these levels.
Plain English
A height in the sky where the air is being squeezed at a particular pressure. The higher you go, the less the air weighs above you, so the pressure drops. Pick a pressure value and there is a matching height for it.
Context Anchor
Seen in sensitive altimeter discussions, especially when learning how pressure changes with altitude and weather.
Derivation
From Latin pressura, 'a pressing,' and level, from Latin libella, 'a small balance' or 'horizontal line.' Together it means a horizontal layer in the atmosphere defined by how hard the air is pressing.
Why Pilots Care
Accurate understanding ensures correct altimeter settings and safe vertical separation between aircraft at assigned flight levels.
Grounding Statement
At any moment, you can imagine the atmosphere as stacked invisible layers, each one marking where the pressure has dropped to a specific value.
Intuition Check
Do not assume “level” means a fixed, flat height above the ground. Here, a pressure level means a place in the atmosphere with a particular pressure value, and that place can move up or down as conditions change.
Example Sentence 1
As the aircraft climbed, it passed through each pressure level until it reached cruise altitude.
Example Sentence 2
At the assigned pressure level the altimeter indicated the correct altitude once the correct setting was applied.