Definition of "duke"

duke

/djuːk/

noun
plural dukes
1. The male ruler of a duchy (female equivalent: duchess).
2. The sovereign of a small state.
3. A high title of nobility; the male holder of a dukedom.
4. A grand duke.
5. Any of various nymphalid butterflies of the Asian genera Bassarona and Dophla.
6. (slang, usually in the plural) A fist.
  Quotations
  “Your friend sure knows how to use his dukes. Biff, bang! One, two, and the copʼs on his ass!”
  1952, Ralph Ellison, Invisible Man, Penguin Books (2014), page 438
  "How did the sport go.""O sparred a few rounds. Let the instructor have a few on the button.""You must be tough.""I can handle my dukes."
  1963, J P Donleavy, A Singular Man, published 1963 (USA), page 19
verb
third-person singular simple present dukes, present participle duking, simple past and past participle duked
1. (transitive, informal) To hit or beat with the fists.
  Quotations
  It seems that PI Rainer was duked by his wife […] .
  2003, John A. Dinan, Private Eyes in the Comics, page 65
2. (slang, transitive) To give cash to; to give a tip to.