This ain't no freestyle battle
All you niggas getting killed with your mouths open
“This ain’t no freestyle battle” refers to the fact that Biggie is widely regarded as a better freestyler than Tupac. Tupac is saying that who’s better at freestyle rap is irrelevant here. He’s not going to “kill” you, he’s going to (literally) kill you!
The fact that his victim has his “mouth open” indicates that they will be talking shit about Pac when they get smoked.
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