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To forcefully encroach upon or interfere with (someone or something). In this town, any business that begins to see a profit will have the mafia muscling in before long. Jake must think I'm trying to muscle in, judging by the way he's been disparaging me to the boss lately.
muscle in (on someone or something)
to try forcefully to displace someone or take over someone's property, interests, or relationships. Are you trying to muscle in on my scheme? If you try to muscle in, you'll be facing big trouble.
Also, muscle in on. Forcibly intrude on or interfere with something, as in The children were determined not to allow the school bully to muscle in, or No more muscling in on our policy decisions! [Colloquial; 1920s]