> The character 囍 means "double happiness" literally, and is often used in wedding ceremonies among other places here in China.
It's used by being hung on the wall, like a painting[1]. Like I said, it has no linguistic use, and thus it is not part of a writing system, which puts it outside the stated scope of Unicode. It is the exact equivalent, for weddings, of the upside-down 福 character that is hung for New Year's, or the wreath that Americans hang for Christmas.
But it does not correspond to anything in any language; there is no Chinese sentence whose spelling would include 囍. Note that the 新华 dictionary entry says "Double 喜. Generally used at happy occasions such as weddings.", and there are zero examples of the character being used. ( https://zidian.aies.cn/NDQ4MA==.htm )
The wording of the 新华 entry is almost identical with the beginning of the 汉语大词典 entry, and it's instructive to quote the rest of the entry:
> Character used at happy occasions. Commonly called "double 喜"[2]. Generally used at occasions such as weddings. Often cut from red paper (or gold leaf), or written on red paper, [then] pasted onto a door, window, or wall, in order to indicate a happy occasion.
[1] Actually, a much closer comparison would be the traditional magical talismans that use elements from the writing system in a freeform way to express various desired goals. https://en.wikipedia.org/wiki/Fulu
[2] This dictionary is nice enough to make the fact completely explicit that 双喜 is the name of the character rather than a definition. 汉语大词典 doesn't even attempt to provide a definition for this character.