Definitions for "Paranasal sinus"
a mucus-lined air cavity in a skull bone; communicates with the nasal cavity; the paranasal sinuses are located in the frontal, maxillary, ethmoid, and spenoid bones
any of the paired sinuses in the bones of the face adjacent to the nasal cavity that are lined with mucous membrane that is continuous with lining of the nasal cavities
sinuses surrounding the nose that help to warm and moisten inhaled air.