1. a large military unit in ancient Rome
Usage: historical
2. a very large number of people or things

1. very numerous; existing in large numbers
Usage: formal

Examples

• Caesar commanded several Roman legions during his conquest of Gaul.
• A legion of fans waited outside the concert hall.
• The problems with the old system were legion.
• Legions of volunteers helped clean up after the hurricane.
• The ancient Roman legion was a formidable fighting force.
• Her admirers are legion throughout the country.
• The company faced legion complaints about their new product.