Definition
The airspeed at which total drag on an airplane is at its lowest value. At this speed, the sum of induced drag (drag from producing lift) and parasite drag (drag from the airframe moving through the air) is minimized, which also corresponds to the speed for maximum lift-to-drag ratio (L/Dmax).
Plain English
The speed at which the airplane meets the least amount of total air resistance. Flying at this speed gives the most efficient flight — the airplane gets the most distance for the least energy.
Context Anchor
Seen in airplane performance discussions, especially when studying glide performance, drag curves, and efficient airspeeds.
Derivation
From 'Velocity' (speed) and 'Minimum Drag' (the lowest amount of total air resistance). The term simply names the speed at which drag bottoms out.
Why Pilots Care
Flying at this speed yields the greatest glide distance after engine failure and the best fuel efficiency for a given distance in unpowered flight.
Grounding Statement
At VMD, the airplane is not so slow that it has to work hard to stay flying, and not so fast that pushing through the air creates extra resistance.
Intuition Check
VMD is not the slowest safe speed. It is the speed where total drag is lowest.
Example Sentence 1
After the engine quit, the pilot pitched for VMD to stretch the glide toward the nearest airport.
Example Sentence 2
During cross-country planning the student used VMD to calculate the maximum distance the airplane could travel with the remaining fuel.