sir

Multiple Entries:
  sir    Sir.  

Concise Oxford English Dictionary © 2008 Oxford University Press:
sir/sɜː(r)/

▶noun

• 1 a polite or respectful form of address to a man.

• 2 used to address a man at the beginning of a formal or business letter.

• 3 used as a title before the forename of a knight or baronet.

– origin ME: reduced form of sire.

Concise Oxford English Dictionary © 2008 Oxford University Press:
Sir.

▶abbreviation (in biblical references) Sirach (Apocrypha).