plunge vs engross

plunge is a noun but engross is not a noun.

Word	Noun	Adjective	Verb	Adverb
plunge	Yes	No	Yes	No
engross	No	No	Yes	No

As verbs, plunge and engross are synonyms defined as:

Other synonyms of plunge include absorb, engulf, immerse, soak up, steep.

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

plunge (verb)	engross (verb)
begin with vigor	consume all of one's attention or time
devote (oneself) fully to	devote (oneself) fully to
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