Meaning of SR in English

Note: in AM, use 'Sr.'

Sr is a written abbreviation for Senior , and is written after a man’s name. It is used in order to distinguish a man from his son when they both have the same name.

...Donald Cunningham, Sr.

Collins COBUILD Advanced Learner's English Dictionary.      Английский словарь Коллинз COBUILD для изучающих язык на продвинутом уровне.