is the act of telling your opinion about something you totally have no idea about, so instead of saying I don't know, you start fessa.
John has started fessa, let's get out of here!
Literal translation: heavy pu**y. Italian slang used to depict a strong independent woman who is serving (instead of saying “girl with the balls” which might sound sexist).
Did you see Beyoncé’ last performance? She’s such a Fessa Pesante