Definition
The lowest altitude, expressed in feet above mean sea level (MSL), to which descent is authorized on final approach or during circle-to-land maneuvering in execution of a non-precision instrument approach for which no electronic glide slope is provided. Descent below MDA is not permitted unless the required visual references are in sight and the aircraft is in a position to land using normal maneuvers.
Plain English
On a non-precision approach (one without a vertical guidance beam), MDA is the floor — the lowest altitude you are allowed to descend to while looking for the runway. You stay at or above this altitude until you can see what you need to see to land safely.
Context Anchor
Seen on instrument approach charts and in instrument flying discussions, including situations where a pilot must fly by instruments to get safely back to visual conditions.
Derivation
Minimum (lowest allowed) + Descent (going down) + Altitude (height above sea level). The phrase tells you exactly what it is: the lowest altitude you may descend to on this kind of approach.
Why Pilots Care
It ensures safe obstacle clearance while giving you the best chance to see the runway and land or execute a missed approach.
Intuition Check
Do not treat MDA as a suggested altitude or a goal to pass through. It is a lower limit unless the required outside view is available for landing.
Example Sentence 1
Descending on the VOR approach, the pilot leveled off at the MDA of 1,240 feet and continued toward the missed approach point while looking for the runway.
Example Sentence 2
If the required visual references were not visible at the MDA, the crew immediately initiated the missed approach.