takeoff booster vs booster unit

takeoff booster and booster unit both are nouns.

Word	Noun	Adjective	Verb	Adverb
takeoff booster	Yes	No	No	No
booster unit	Yes	No	No	No

As nouns, takeoff booster and booster unit are synonyms defined as:

takeoff booster and booster unit: the first stage of a multistage rocket

Other synonyms of takeoff booster include booster, booster rocket, takeoff rocket.

takeoff booster (noun)	booster unit (noun)
the first stage of a multistage rocket	the first stage of a multistage rocket