a hoi hoi - A way to greet someone that's way more fun than just saying

A way to greet someone that's way more fun than just saying hi. It’s like the most basic form of coolness.

I said "Hoi hoi!" to my friend and he said hi back.

My teacher said "Hoi hoi!" and I got confused.

I used "Hoi hoi!" to greet my dog and it wagged its tail.