sir

noun8

1. •
   a respectful word for a man, used when speaking to him, especially if his name is not known

   • Excuse me, sir, do you know the way to the art museum?
2. •
   A respectful term of address to a man of higher rank or position.
3. •
   to a superior military officer.

   • Sir, yes sir.
4. •
   to a teacher.

   • Here's my report, sir.
5. •
   (Philippines, informal) A respectful term of address or reference to a man of higher rank or position before the man's given name or nickname.
6. •
   (UK) The titular prefix given to a knight or baronet.
7. •
   to a knight or other low member of the peerage.

   • Just be careful. He gets whingy now if you don't address him as Sir John.
8. •
   A man of a higher rank or position.

verb1

1. •
   (informal) To address another individual using "sir".

   • Sir, yes, sir! —Don't you sir me, private! I work for a living!

adjective1

1. •
   Initialism of susceptible-infected/infectious-removed/recovered.

noun2

1. •
   Initialism of surface insulation resistance.
2. •
   Abbreviation of silent information regulator.