Learner's definition of MR.
— used as a title before the name of a man
see also messrs.
How are you, Mr. Jones?
Mr. John Doe
— used as a title when speaking to a man who has an honored position or office
— used as part of a title for a man who has won a contest
— used to refer to a man who is very successful and famous for a particular activity (such as a sport) or who has a particular quality