verb
plunges; plunged; plunging
[no obj]
always followed by an adverb or preposition :to fall or jump suddenly from a high place
to fall or drop suddenly in amount, value, etc. :plummet
always followed by an adverb or preposition :to have a steep slope or drop downward
plunge in/into
[phrasal verb]
plunge (something) in or plunge (something) into (something) :to push (something) into (something) quickly and forcefully
plunge in or plunge into (something) :to start doing (something) with enthusiasm and energy
a plunge into (something) :to suddenly begin to be in (a particular and usually bad condition or situation)
b plunge (someone or something) into (something) :to cause (someone or something) to suddenly be in (a particular condition or situation)
noun
plural plunges
[count] a sudden fall or jump usually from a high place
a sudden quick fall in amount, value, etc.
the act of suddenly beginning to be in a particular condition or situation - usually + into
take the plunge
informal :to do something after thinking about it especially for a long time