Final answer:
A trustbuster is someone who opposes powerful trusts controlling the entire market, and aims to break up or regulate them for fair competition.
Step-by-step explanation:
A trustbuster is someone who does not want powerful trusts to control the entire market. It refers to individuals or government officials who aim to break up or regulate large, monopolistic corporations in order to promote fair competition and prevent market dominance. Theodore Roosevelt, for example, was known for his efforts in curbing the power of trusts during his presidency.
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