Great courage, especially the kind shown in war or in serious danger. It is a formal, respectful, slightly old word — the word on medals and monuments, not the word you use about daily life. Soldiers are decorated 'for valour'; a country honours 'acts of valour' by firefighters or police. The most common place learners meet it is a famous saying from Shakespeare: 'discretion is the better part of valour', which means the truly brave thing is sometimes to be careful and not fight. People still say that today, usually with a smile, when they decide to walk away from trouble. Spelling depends on where you are: valour in Britain, Australia and Hong Kong; valor in the United States. The adjective is valiant, and the everyday, all-purpose word for the same idea is courage or bravery. Use those unless the situation is grave.