How you guys define toxic, what kind of words can be seen as toxic?

I have a game where I just come to practice new champ top Annie, and I am a little bit lag, I didn't blame anyone just told truth that my JG is pretty bad, I said he is stupid and even my teammate agreed with me, but the enemy top side kept being toxic and said the words like trash and so on. After the game, I got punishment and he didn't. Now I wonder, how you guys define toxic and how the Riot system working ?? Compare between stupid and trash, which one is really toxic? And I swear I didn't say any other rude words except stupid.
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