[ there's a pause as he gets up for a few moments, but he returns very obviously thumbing through the pages of a book and clearing his throat. ]
Tantrum, noun: "An uncontrolled outburst of anger and frustration, typically in a young child." Synonyms are listed as: conniption, fit, scene, tirade, and— ah! Would you look at that: rant.
[ vriska has no way of knowing whether or not he's actually reading straight from a dictionary, but, spoiler alert: he isn't. the book noises are strictly for effect. ]