Definition
The sum of all aerodynamic drag forces acting on an airplane in flight, made up primarily of induced drag (drag produced as a by-product of lift) and parasite drag (drag from the airplane's shape, surface friction, and air being pushed aside). Total drag varies with airspeed and configuration, and at any given airspeed it is the single force that thrust must overcome to maintain steady flight.
Plain English
All the drag on the airplane added together. It's everything slowing the airplane down, combined into one number.
Context Anchor
Seen in takeoff, climb, performance, and ground effect discussions, especially when explaining why an airplane may lift off easily near the runway but need more speed to climb away safely.
Derivation
Total comes from a Latin word meaning whole or entire. Drag is an older English word connected with pulling or drawing something along. Together, total drag means the whole pulling-back effect of the air on the airplane.
Why Pilots Care
Reductions in total drag near the ground improve acceleration and climb performance; pilots must anticipate the opposite effect when leaving ground effect.
Grounding Statement
Just above the runway, the airplane may feel easier to keep flying because total drag is lower; a few feet higher, that drag can increase again.
Intuition Check
Do not read total drag as one single kind of drag. It means all the different sources of drag added together.
Example Sentence 1
In ground effect just after liftoff, induced drag is reduced, so total drag is lower and the airplane can accelerate more quickly.
Example Sentence 2
After liftoff, as the airplane climbs out of ground effect total drag rises again and the pilot must adjust pitch to maintain the desired climb speed.