Used when someone decides to do something that might be risky or requires a lot of courage. He's always wanted to travel the world, so he took the plunge and bought a one-way ticket.
Pro Tip 2/3
Major Change
Often related to life-changing decisions or significant new beginnings. They took the plunge and moved to another country for a fresh start.
Pro Tip 3/3
Emotional Nuance
Conveys a sense of excitement mixed with apprehension about the outcome. I took the plunge and finally asked for the promotion I felt I deserved.