An occurrence in which something or someone plunges(noun)
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Use "plunging" in a sentence
"Could he feel the tension in my chest that brought his name plunging through my lips in a harsh whisper?"
"Mr. Verhovek zeroes in on the mid-1950s, when Comets first seemed to own the world and then started plunging from the sky in pieces."
"The big motor car waited at the station, and Frederick Travers thrilled as he always thrilled to the distant locomotive whistle of the train plunging down the valley of Isaac Travers River."