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