sustainer

About 0.17 uses per million words.

Meaning

1. noun A person or thing that sustains.
2. noun A rocket engine that remains with a spacecraft during its ascent after the separation of the booster engines.
3. noun A person who makes regular donations, especially to a public radio or television station.
4. noun A radio program without a commercial sponsor.

Similar words

sustentator cosustainer maintainer stayer subsister supporter stabilizer upholder nourisher substantiator

Often followed by

of and engine is motor in stage rocket