plunge vs start out

plunge is a noun but start out is not a noun.

Word	Noun	Adjective	Verb	Adverb
plunge	Yes	No	Yes	No
start out	No	No	Yes	No

As verbs, start out is a hypernym of plunge; that is, start out is a word with a broader meaning than plunge:

Other hypernyms of plunge include begin, commence, get, get down, set about, set out, start.

plunge (noun)	start out (noun)
a brief swim in water
a steep and rapid fall

plunge (verb)	start out (verb)
begin with vigor	take the first step or steps in carrying out an action
devote (oneself) fully to	depart for someplace
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