jack flagn.
/ˈdʒak flaɡ/, U.S. /ˈdʒæk ˌflæɡ/ A ship's flag of a smaller size than the ensign, used at sea as a signal, or as an identifying device. More commonly known as jack (see jack n.4).
ΚΠ
1655 Instr. Capt. Wm. Goodson 10 Oct. in State Papers Domestic Civil War & Interregnum (P.R.O.: SP 25/76A) 156 You shall weare the Jack fflagge at the main top Masthead.
1720 J. Burchett Compl. Hist. in Mariner′s Mirror (1911) 1 101 There were some doubts whether his Lordship..should have borne at the Main topmast head the Royal Standard of England, or the Union, or, more properly speaking in Maritime phrase, the Jack Flag.
1878 Notes & Queries 4 May 350/1 The ‘jack flag’ of the English navy was a plain white flag bearing a red St George's cross.
1968 Pacific Stars & Stripes 9 Sept. 24 The jack flag and the American flag were hoisted as the Navy Band from Washington played the national anthem.
1986 Motor Boating & Sailing July 107/2 They never miss a Sunday or holiday without setting the Jack Flag when at anchor.
This entry has been updated (OED Third Edition, March 2018; most recently modified version published online March 2022).
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n.1655