v.1. To fall or dive into some place or thing: I jumped off the diving board and plunged into the warm water.
2. To thrust or throw something forcefully into some place or thing: I plunged the shovel into the soil.
3. To enter earnestly or wholeheartedly into some activity or situation: After the vacation, I plunged into my studies with renewed energy.
4. To send someone or something into some condition or situation: My gambling losses plunged me into debt.
5. To fall into some state or condition: After my divorce, I plunged into a deep depression.