B1
a teacher of the highest rank in a department of a British university, or a teacher of high rank in an American university or college
Dictionary examples:
The English professor corrected the grammar on his birthday cake. (0.0)
The music professor's ringtone was a full symphony orchestra. (0.0)
The chemistry professor's coffee mug was labeled 'Do not drink'. (0.0)
Professor Stephen Hawking (4.2)
a sociology professor (50.6)
a professor of sociology (51.0)