Plain English Meaning
Choosing to land somewhere other than where you originally planned, because something has changed and the new airport is the safer or smarter choice.
Full Definition
A change of flight plan to a destination other than the originally intended airport, made in response to a condition that makes continuing to the planned destination unsafe or impractical — such as an inadvertent icing encounter, deteriorating weather, a mechanical issue, or a medical emergency.
Context Anchor
In an inadvertent icing encounter, a pilot may need a flight diversion to leave icing conditions or land at a safer airport.
Derivation
From the Latin divertere, meaning 'to turn aside.' A diversion is literally turning the flight aside from its planned path to a different airport.
Why Pilots Care
A diversion requires recalculating , updating , and ensuring the can be reached safely, directly impacting in icing conditions.