union jack

Noun capitalized: Union Jack

Union Jack (plural Union Jacks)

1. The flag of the United Kingdom, consisting of the flags of England (St. George's Cross), Scotland (St. Andrew's Cross), and Ireland (St. Patrick's Cross, now only used in Northern Ireland) combined.
   • When the wedding started I found a spot near Windsor Castle’s entrance, where I could watch the ceremony on a big screen. People who line the roads at weddings are, by definition, the most die-hard royalists, and all the usual figures were out in force: the men bellowing and ringing bells in the...2018 May 20, Hadley Freeman, “Is Meghan Markle the American the royals have needed all along?”, in The Guardian
2. (broadly) The British Empire.
   • Settlers already fearing the possibility of seeing their 1600, sometimes 1700 percent, profit margins stripped from them by London’s abolitionism saw no other option but to secede from the Union Jack.2019, Danny Haiphong, Roberto Sirvent, chapter 3, in American Exceptionalism and American Innocence, New York: Skyhorse Publishing, →ISBN, page 81
3. (UK) The flag, consisting of the flags of England, Scotland, and Northern Ireland combined, flown on ships of the government of the United Kingdom.
4. (US) The flag, consisting of the blue star-studded field in the corner of the national ensign, flown at the jackstaff by ships at anchor.