sinus: Meaning and Definition of

si•nus

1. a curve; bend.
2. a curving part or recess.
1. any of various cavities, recesses, or passages, as a hollow in a bone, or a reservoir or channel for venous blood.
2. one of the hollow cavities in the skull connecting with the nasal cavities.
3. an expanded area in a canal or tube.
4. a narrow passage leading to an abscess or the like.
5. a small, rounded depression between two projecting lobes, as of a leaf.