Bob Moore wrote:

25.121(d) at maximum takeoff weight

This is how it was explained to me; an ex-member of our club that flies for
"a major" simplified it to "one-engine-out missed approach": if the plane
can do that at t/o weight, no dump system required.

This is distinct from the maximum landing weight, which involves other
factors. In an emergency, therefore, a pilot might need to make an
"overweight landing".

- Andrew