All 4 Uses

dissertation
in
Educated, by Tara Westover
(Edited)

I wrote an essay on John Stuart Mill's concept of self-sovereignty, and my supervisor, Dr. David Runciman, said that if my dissertation was of the same quality, I might be accepted to Cambridge for a PhD.
p. 267.2

dissertation = a scholarly paper required for an advanced academic degree
I set to work on my dissertation, again choosing Mill as the topic.
p. 267.3
My dissertation gave a different shape to history, one that was neither Mormon nor anti-Mormon, neither spiritual nor profane.
p. 318.3
On my twenty-seventh birthday, the birthday I had chosen, I submitted my PhD dissertation.
p. 318.9 *

dissertation = scholarly paper required for an advanced academic degree

editor's notes: You might recall that Tara's parents didn't remember or record her birthday.

Definitions:

(1) (dissertation)
a lengthy academic paper -- especially a scholarly work required for an advanced academic degree
(2) (meaning too rare to warrant focus)