n. A master; lord; sovereign.n. A person of rank or importance; a personage; a gentleman.n. Master; mister: a respectful and formal title of address, used formerly to men of superior rank, position, or age, and now to men of equal rank, or without regard to rank, as a mere term of address, without etymological significance.n. Specifically— A title of honor prefixed to the Christian names of knights and baronets, and formerly applied also to those of higher rank, as the king; it was also prefixed occasionally to the title of rank itself: as, Sir King; Sir Knight; Sir Herald.n. (b ) Formerly, a title of a bachelor of arts; hence, a title given to a clergyman; also, a clergyman.To address as “sir.”To use the word sir.n. A Persian measure of weight, equal to 16 miskals or ounces troy.