Jack staff

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(Naut.) a staff fixed on the bowsprit cap, upon which the jack is hoisted.

See also: Jack

Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.
References in periodicals archive ?
JACK STAFF (DEVELOPMENT) | Loan value: PS25,000 | Amount recouped: Zero | Negative balance: PS25,000 This is understood to be a television project.
The Union Flag is flown on the Jack Staff at the bow of all Royal Navy vessels when in port, which makes it a maritime flag.
The flag's use at sea probably resulted in the word "Jack" being added to the name Union flag, because it was usually flown at the bow end of the ship, from what was known as the jack staff.
Basics THE magnificent flag, which measures 224cm x 356cm, was flown from the jack staff of HMS Spartiate during the Battle of Trafalgar.