Definitions

1. noun

A hollow space or cavity within a bone, especially one of the paired air-filled cavities in the skull that are connected with the nasal passages.

“The doctor examined her sinuses to determine the cause of her chronic congestion.”

2. noun

A curve or bend in a channel, river, or coastline.

“The sailors navigated their boat through the narrow sinus in the rocky coastline.”

3. verb

To strain or exert in a particular way.

“The horse had to sinus its muscles to climb the steep hill.”