Definition of "die off"

die off

verb
third-person singular simple present dies off, present participle dying off, simple past and past participle died off
1. To suffer a series of deaths; to die one by one; to progressively become extinct. (If a group of plants, animals, or people dies off, the entire group dies over a period of time.)
2. To become defunct or nonexistent.
3. Of music, noise, etc., to reduce in volume until no longer audible.