Plain English Meaning
The number of people getting on planes at an airport during a set time, usually counted per year. It's how busy an airport is measured by passengers boarding.
Full Definition
The total count of passengers boarding aircraft at a given airport over a specified period, used by the FAA as a primary measure of an airport's traffic volume and a factor in airspace and airport classification.
Context Anchor
Seen in FAA airspace and airport discussions when describing how busy an airport is and why certain controlled airspace may be established around it.
Derivation
From 'enplane,' built on the model of 'embark' -- the prefix 'en-' meaning 'to put into or onto,' plus 'plane.' So an enplanement is literally the act of putting a passenger onto a plane. Knowing this makes the term less bureaucratic: it just means a boarding.