The 'Union Flag' or the UK is commonly (and incorrectly) called the Union Jack. A jack is a small flagpole on the front of a ships. This is where the Union Flag is flown on Royal Navy ships, hence a flag used for that specific purpose is called a Union jack flag. All other usage, other than naval, should refer to it as the 'Union Flag'.
Interestingly enough, the Union Flag is not the official national flag of the UK, because the UK does not have a legally defined national flag. It is just commonly accepted as being so.
The jack refers to the jackstay of a ship, on which the Union Jack would be displayed. Strictly speaking the flag should be called the Union Flag, but Union Jack is well known. Actually, the union jack is what the flag is called out at sea, but the union flag is what they call it on land.
It commonly known as the Union Jack, although its proper name is the Union Flag.
The nickname for the British flag is the Union Jack. Although it is only correctly known as this when flown on a ship.
The Union Jack - properly known as the Union Flag.
Union Flag, or more casually the Union Jack
I'm not sure what you mean by 'special name', but the official name for the British flag is: Union Jack
Red, White and Blue. It is known as the Union Flag, or sometimes erroneously as the Union Jack.
The Union Jack, also known properly as the Union Flag.
the Union Jack
The Union Flag, it is only correctly termed the 'Union Jack' if it is raised on board a ship.
The Union Jack is the nickname of the UK flag.
The Union Flag commonly known as the Union Jack is the blue, white and red flag of the UK.