1 descend, drop, plummet, dive, pitch, nosedive, fall (headlong):
They lost their footing, and both Holmes and Moriarty plunged into the abyss
2 submerge, sink, immerse; engulf, overwhelm:
I plunged my hand in the icy water to retrieve the keys. She plunged herself into her work to try to forget him.
3 dive, nosedive, fall, pitch, plummet, drop, descent; submersion, immersion:
After the scandal his career took a plunge from which it never recovered. Every winter they take a plunge into the icy waters of the Serpentine
4 gamble, wager, bet, risk:
Are you taking the plunge with an investment in South America?