Meaning of “formation” - Learner’s Dictionary

formation

noun uk us /fɔːˈmeɪʃən/
DEVELOPMENT [ U ]

the development of something into a particular thing or shape:

the formation of a crystal
SHAPE [ C, U ]

the particular shape of something or the way things are arranged:

rock/cloud formations
The planes flew overhead in formation (= in a pattern).

(Definition of “formation” from the Cambridge Learner’s Dictionary © Cambridge University Press)