Definition
The lowest takeoff decision speed at which the airplane can still maintain directional control and continue the takeoff safely after the failure of the most critical engine. Below this speed, a rejected takeoff is the required action because the airplane cannot reliably continue flying on the remaining engine(s).
Plain English
The slowest speed at which a multi-engine airplane can lose an engine during the takeoff roll and still keep going safely. If an engine fails before the airplane reaches this speed, the pilot must stop on the runway instead of trying to fly.
Context Anchor
Seen in rejected takeoff and takeoff performance planning, especially when comparing whether to stop or continue after a problem during the takeoff roll.
Derivation
V1 comes from the aviation convention of labeling key takeoff speeds with V (for velocity) and a number. V1 is the takeoff decision speed. 'Minimum V1' simply identifies the lowest acceptable value of that decision speed for a given takeoff.
Why Pilots Care
It sets the lower limit for a safe go/no-go decision and prevents runway overruns when an engine fails early in the takeoff roll.
Intuition Check
Minimum does not mean “best” or “most conservative” by itself. Here it means the lowest V1 value allowed before continued-takeoff performance becomes unacceptable.
Example Sentence 1
The crew calculated minimum V1 during preflight planning to confirm the runway was long enough for a safe rejected takeoff if an engine failed early in the roll.
Example Sentence 2
An engine failure below minimum V1 requires an immediate rejected takeoff.