1. most important; chief; principal

1. the chief or most important part
2. a principal pipe or cable in a utility system
3. the open ocean
Usage: nautical

Examples

• The main reason for the delay was bad weather.
• What’s the main idea of this paragraph?
• The main course will be served after the salad.
• In the main, I agree with your proposal.
• A water main burst on Fifth Street.
• The ship sailed into the main at dawn.
• The main entrance is around the corner.