Hedge fund /hɛdʒ fʌnd/ (n.)
A couple of guys with a bright idea and a rented office in Mayfair. The Oxford English Dictionary says it is an “offshore investment fund, typically formed as a private limited partnership, that engages in speculation using credit or borrowed capital.”
They also like shorting. This was a more fun game before the world got rocked on its axis by people on Reddit, and the Wikipedia effect came to the financial services market.