rant about (something)
To speak angrily, forcefully, and at great length about something. I hate going to my friend's house because his husband always rants about politics at me. I stopped paying attention as soon as he started ranting about being more fiscally responsible.
rant (at someone) about someone or something
to talk in a loud, violent way, about someone or something. Anne ranted about the bad service she had received at the store. On the bus, someone was ranting at me about the end of the world.