Plain English Meaning

When you have a cold or congestion, the small openings that let air move in and out of your sinuses can get blocked. If the pressure outside changes (like during descent) and the air trapped in your sinus can't equalize, it causes intense pain in your face or forehead.

Full Definition

A painful condition in which the air pressure inside one of the pilot's sinus cavities cannot equalize with the changing pressure of the surrounding cabin air, usually because a cold, allergy, or sinus infection has swollen or congested the passage that normally allows air to flow in and out of the sinus. It most often occurs during descent and can produce sharp facial pain, pressure around the eyes or cheeks, and sometimes nosebleed.

Context Anchor

Seen in aeromedical discussions about flying with a cold, allergies, or sinus congestion, especially before flights involving altitude changes.

Derivation

From Latin sinus meaning a hollow or , referring to the air-filled spaces in the bones of the face and skull. 'Block' here means a blockage of the small passage connecting that cavity to the nose, trapping air inside.