It's another word for a flag. Usually a jack is flown on the jackstaff of a ship, but in reference to the Union flag it's commonly used to describe the flag. If we were to be absolutely correct, the...
Supposing it is the British Union Flag that you are talking about, it's composition represents the Union of Britain, Scotland and Northern Ireland and it consists of the national religious symbols of...
Jacks are additional national flags flown by warships (and certain other vessels) at the head of the ship. These are usually flown while not underway and when the ship is dressed on special...