In a frenzy, people go into a state of hysteria. Stay away from hungry sharks or kids at a 16th birthday party when the pizza arrives if you don't want to get caught up in a feeding frenzy.
Frenzy is derived from the Latin word phreneticus meaning "delirious." If you're in a frenzy, you're certainly delirious. You can be in a frenzy because something made you mad, happy, or even just hungry — whatever makes you so crazy you're not thinking clearly. Frenzy is often used when talking about a group of people (or animals) who get worked up at the same time about the same thing, like sharks near tasty fish or teenagers near pizza.