set about vs plunge

set about is not a noun while plunge is a noun.

Word	Noun	Adjective	Verb	Adverb
set about	No	No	Yes	No
plunge	Yes	No	Yes	No

As verbs, plunge is a hyponym of set about; that is, plunge is a word with a more specific, narrower meaning than set about:

set about (noun)	plunge (noun)
	a brief swim in water
	a steep and rapid fall

set about (verb)	plunge (verb)
take the first step or steps in carrying out an action	begin with vigor
enter upon an activity or enterprise	devote (oneself) fully to
begin to deal with	cause to be immersed
	immerse briefly into a liquid so as to wet, coat, or saturate
	thrust or throw into
	fall abruptly
	drop steeply
	dash violently or with great speed or impetuosity