A man of a higher rank or position. / to a knight or other low member of the peerage. / to a superior military officer. / to a teacher.

To address (someone) using "sir".

Alternative letter-case form of sir. / (Britain) The titular prefix given to a knight or baronet.

(manufacturing) Initialism of surface insulation resistance. / (biochemistry, genetics) Abbreviation of silent information regulator.

(epidemiology) Initialism of susceptible-infected/infectious-removed/recovered.

Abbreviation of Sirach.

plural of sir

Third-person singular simple present indicative form of sir

present participle of sir

simple past tense and past participle of sir