1. a raincoat, especially a waterproof coat
Usage: informal; chiefly British
2. used as a form of address for a man whose name is unknown
Usage: informal; chiefly American

Examples

• I grabbed my mac before heading out in the rain.
• Don’t forget your mac – it looks like it might pour.
• Hey mac, you dropped your wallet back there.
• Listen here, mac, that’s not how we do things.
• The old mac kept him dry during the storm.
• Excuse me, mac, do you know what time it is?