1. a hollow space or cavity within a bone or other tissue, especially in the skull connecting with the nostrils
Usage: anatomy
2. a recess or indentation in a coastline, forming a bay
Usage: geography

Examples

• The doctor examined her sinuses to check for infection.
• Blocked sinuses can cause headaches and facial pain.
• Cold weather often makes my sinuses feel congested.
• The medication helped clear his sinus passages.
• She had surgery to repair her damaged sinus cavity.
• The coastal sinus provided a natural harbor for boats.