If you've ever heard an early morning bugle alongside a flag being raised, you know exactly what reveille sounds like. It's meant to wake everyone up in a patriotic way.
This word is a modification of French imperative réveillez, which means wake up, or "Awaken!" Appropriately, the noun reveille refers to a bugle call meant to accomplish exactly this. Reveille most often occurs at sunrise in a military encampment or base when a bugler plays a familiar tune to wake up the military personnel.