Definition of sinus noun from the Oxford Advanced Learner's Dictionary



BrE BrE//ˈsaɪnəs//
; NAmE NAmE//ˈsaɪnəs//
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any of the hollow spaces in the bones of the head that are connected to the inside of the nose blocked sinuses Word Originlate Middle English (in the medical sense): from Latin, literally ‘a recess, bend’.
See the Oxford Advanced American Dictionary entry: sinus