Plain English Meaning
How an aircraft flies through the air — how well it lifts, how cleanly it cuts through the air, how it handles, and at what point it stops flying smoothly.
Full Definition
The set of properties that determine how an aircraft (or a part of it, such as a wing) behaves as air flows over and around it — including how much lift it produces, how much drag it creates, how it stalls, and how it responds to control inputs at various speeds and angles of attack.
Context Anchor
Seen in structural icing discussions when describing how ice on the airplane changes performance and handling.
Derivation
From Greek 'aero' (air) and 'dynamis' (power, force). literally refers to the forces of moving air. 'Characteristics' means the distinguishing features of something. Together: the behaviour produced by air moving over the aircraft.