The term "Union Jack" is not considered correct because a Jack is a flag flown from a ship and British merchant ships fly the Red ensign and the Royal Navy flies the White Ensign. The Official title of the Flag of the United Kingdom is the "Union Flag" and unoffically "British Flag" although this term might be considered controversial in Northern Ireland
I'm not sure what you mean by 'special name', but the official name for the British flag is: Union Jack
Union Flag, or more casually the Union Jack
Union Jack
union jack
Jack is another name for a flag, usually a small flag used for signaling, but in the case of the Union Jack it symbolises the union of the three countries - England, Wales, Scotland
The Union Jack
the union is the part where all the flags of the 3 flags are together. being Northern Ireland, England and Scotland
Union means exactly that - a union, in this case of England, Scotland and Wales. Jack is another name for a flag. A jack is a particular kind of flag.
The Union Jack or Union Flag to give it its proper name, is an amalgamation of the flags of England, Scotland and Northern Ireland.
Union Jack
The Union Jack is the nickname of the UK flag.
The Union Jack / The Union Flag :)