Plain English Meaning
The exact spot on a wing, propeller blade, or other surface where the oncoming air comes to a complete stop and then divides — some going over the top, some going under the bottom.
Full Definition
The point on a body in a moving airflow where the local airflow velocity is zero. Air striking the body splits at this point and flows around either side of it. Because the airflow is brought to rest, static pressure at the stagnation point is at its highest value for that body in that flow.
Context Anchor
Seen in aerodynamics and airframe discussions about airflow over wings, engine inlets, probes, and other surfaces facing the airflow.