0 a man of very high rank in a country, or the ruler of a small independent country
2 (in some countries) a title of a man who has a very high social rank or who is the ruler of a small, independent country, or the person himself
They claim to be descendants of a French duke.
The order of precedence for titled nobility in Britain is duke, marquis, earl, viscount, baron.
The play revolves round the betrothal of a duke to a doctor's daughter.
Guys get in fights, they duke it out and then it's over and they go have a beer.
The pair first duked it out in 2012.