General slang:
* Starving: This is the most common and widely understood slang for being very hungry.
* Hangry: A combination of "hungry" and "angry," this refers to being irritable due to hunger.
* Famished: This implies a very intense level of hunger.
* Could eat a horse: This is a hyperbole, indicating extreme hunger.
* My stomach is growling: This describes the physical sensation of hunger.
More informal slang:
* I'm starving to death: Another hyperbole, but more dramatic than "could eat a horse."
* I could eat a whole pizza: Similar to "could eat a horse," but with a more specific food.
* My tummy is rumbling: A more playful way of saying "my stomach is growling."
* I'm so hungry I could eat a brick: Another humorous exaggeration.
The best slang to use will depend on the context and your audience.