sinus (pouch or cavity in any organ or tissue)

(medicine) sinus

secondary audio channel in a multiple audio channel television broadcast (音声多重放送), used for commentary, audio in another language, etc.

(film, television) assistant director

(of a committee, society, club, etc.) a vice president, an assistant chairperson

viceroy; one who governs a country, province, or colony as the representative of a monarch.

(Internet slang) sub account; sub

someone of that type, someone who does that

person

(law) warranty against defects