Reveille is the special tune, usually on a bugle or trumpet, that wakes soldiers in the morning. People also use it for the time that tune is played: “Reveille is at five.” It belongs to army and navy life; outside that world you mostly meet it in films, books, or as a joke about an alarm clock. The word is French in origin: from réveillez, the command form of réveiller, “to wake.” English borrowed the idea and the sound, then dropped the accent. Though actually, the hard part is the pronunciation: in British English it is REV-uh-lee, not “re-veil” and not like reveal.