|—n , pl -nuses|
|a. any bodily cavity or hollow space|
|b. a large channel for venous blood, esp between the brain and the skull|
|c. any of the air cavities in the cranial bones|
|2.||pathol a passage leading to a cavity containing pus|
|3.||botany a small rounded notch between two lobes of a leaf, petal, etc|
|4.||an irregularly shaped cavity|
|[C16: from Latin: a curve, bay]|
sinus si·nus (sī'nəs)
A depression or cavity formed by a bending or curving.
A channel for the passage of blood or lymph, without the coats of an ordinary vessel, such as the blood passages in the gravid uterus or in the cerebral meninges.
Any of various air-filled cavities in the bones of the skull, especially one communicating with the nostrils.
A dilatation in a blood vessel.
A fistula or tract leading to a pus-filled cavity.