Jason, why are you being such a skeez?

Skeez is a slang term heard in Mean Girls.

Skeez is a noun. A skeez is the same as a sleaze. It means a sleazy, perverted, or sexually promiscuous person.

This slang was used by Regina George, when she asked Jason why is he being such a skeez, after he attempted to make fun of Cady Heron. Funnily, both of the uses of 'skeez' in the film were directed to Jason.