The term 'Sinus in a Bone' is referring to the maxillary sinus, which is located in the maxilla bone of the skull. The maxillary sinus is also known as the antrum, which is a 6 letter word. The maxillary sinus is one of the paranasal sinuses, which are air-filled cavities located within the bones of the skull and face. They are connected to the nasal cavity and help to humidify and filter the air that passes through the nose.