Both Uses of

resignation
in
Brave New World

After the scene in the Fertilizing Room, all upper-caste London was wild to see this delicious creature who had fallen on his knees before the Director of Hatcheries and Conditioning–or rather the ex-Director, for the poor man had resigned immediately afterwards and never set foot inside the Centre again–
p. 153.5 *

resigned = quit (a job)

"Yes, we're off to-morrow," said Bernard on whose face the Savage remarked a new expression of determined resignation.
p. 242.4 *

resignation = acceptance of something undesired as unavoidable

Definitions:

(1) (resignation as in: submitted her resignation)
to quit -- especially a job or position; or a document expressing such an act
(2) (resignation as in: accepted it with resignation)
acceptance of something undesired as unavoidable or the lesser of evils
(3) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

To resign can also more specifically mean to surrender or give up as in "I was clearly going to lose the chess game, so I resigned;" or "She resigned all pretense."