Barbarous means extremely cruel, brutal, or uncivilized. When people act in barbarous ways, they behave with a violence and cruelty that seems to ignore all human decency. The word describes actions so harsh and savage that they shock our sense of what's right.

History books describe barbarous acts committed during wars, when soldiers treated prisoners with terrible cruelty or destroyed entire cities without mercy. In literature, you might encounter a barbarous villain who torments others without any compassion. When people call something barbarous, they're saying it crosses a line from merely wrong or mean into something far worse.

You might also encounter barbarous used more mildly to describe something shockingly harsh or unrefined, though not necessarily violent. A music teacher might call a student's off-key singing “barbarous” if it's truly awful, though this use is somewhat old-fashioned. The word barbaric means essentially the same thing as barbarous and is more common today.