I could eat a horse
Definition 1 of 1
Pro Tip 1/3Exaggeration
This phrase uses exaggeration to express extreme hunger but isn't meant to be taken literally. 
I missed lunch today, and now I could eat a horse!
Pro Tip 2/3Informal
It's a casual expression, suitable for informal situations, but too colloquial for formal contexts. 
Guys, let's get pizza. I could eat a horse right now!
Pro Tip 3/3Cultural Sensitivity
Some cultures might find the idea offensive. Be mindful of the setting and who you're talking to. 
Be careful saying 'I could eat a horse' in a country where horses are revered.