rah-rah
Indicating an exuberant or passionate enthusiasm (for something). Typically said in reference to school or college pride or spirit. I always find these rah-rah assemblies to be so annoying. As a cheerleader, you're supposed to bring some rah-rah spirit to the people watching our teams play.
hoo-ah
An affirmative exclamation commonly used by members of the US military. The soldiers all shouted "Hoo-ah!" before dispersing.
hoorah
1. An exclamation of celebration; hooray. You got an A on the exam—hoorah!
2. An affirmative exclamation commonly used by members of the US military. The soldiers all shouted "Hoorah!" before dispersing.