1. To become lost to obscurity; to not be known or remembered by anyone. The poet sank into oblivion after the war, only coming back into public awareness after an archive of his works was discovered in the basement of an abandoned warehouse in East Germany. He held a rather cynical view of parenthood, believing that people only had children to avoid sinking into oblivion.

2. To enter into total unconsciousness. The last thing I remember was the doctor asking me to count to ten before the general anesthetic took effect and I sank into oblivion. He was so utterly exhausted that he sank into oblivion the moment my head hit the pillow.