Meaning of “buy sth up” - Learner’s Dictionary

buy sth up

phrasal verb with buy us uk /baɪ/ verb [ T ] past tense and past participle bought

to quickly buy a lot of something, often all that is available:

Most of the land in the area has been bought up by property developers.

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