What does "swan song" mean?

A final performance or accomplishment, especially one before retirement.

What is a synonym for "swan song"?

Common synonyms include: addendum, afterthought, apodosis, appendix, back matter, benefit.

noun

noun ·Moderate ·College level

Noun

1
A final performance or accomplishment, especially one before retirement. idiomatic
"Yet, on the whole, our good Saint-Pierre is musical, poetical though most morbid: we will call his Book the swan-song of old dying France."
2
a final performance or effort (especially before retirement) wordnet

"Yet, on the whole, our good Saint-Pierre is musical, poetical though most morbid: we will call his Book the swan-song of old dying France."

Calque of German Schwanenlied(from Schwan + Lied) or Schwanengesang; from the belief that the mute swan sings before dying.