plunge in (also plunge into something) phrasal verb (see also plunge)

1. to start talking or doing something quickly and confidently, especially without thinking about it first:
It’s a difficult situation. You can’t just plunge in and put everything right.
‘I don’t agree,’ she said, plunging into the conversation.

2. to jump or dive into water:
He stripped off and plunged into the sea.

3. plunge something ↔ in (also plunge something into something) to push something firmly and deeply into something else:
He opened the bag and plunged his hand in.
Plunge the pasta into boiling water.
Repeatedly she plunged the knife into his chest.

[TahlilGaran] Dictionary of Contemporary English ▲