['s??n?s]
¦ noun
1. Anatomy & Zoology a cavity within a bone or other tissue, especially one in the bones of the face or skull connecting with the nasal cavities.
2. Anatomy & Zoology an irregular venous or lymphatic cavity, reservoir, or dilated vessel.
3. Medicine an infected tract leading from a deep-seated infection and discharging pus to the surface.
4. Botany a rounded notch between two lobes on the margin of a leaf or petal.
5. [as modifier] Physiology relating to the sinoatrial node of the heart: sinus rhythm.
Derivatives
sinusitis noun
Origin
ME: from L., lit. 'recess, bend'.