X has 16 different meanings across 6 categories:
Any mark that looks like that letter, such as a mark made by a person who cannot read or write in lieu of a signature.
Ecstasy, a particular street drug.
Cross, crossing.
Intersex or non-binary (in passports and identification documents).
Suitable only for those aged 16 or (later) 18 years and over.
Abbreviation of extreme.
Alternative letter-case form of X (“intersex or non-binary, in passports and identification documents”)
An unknown quantity or unknown value.
A placeholder for an unknown, suppressed or hypothetical name.
Christ
The twenty-fourth letter of the English alphabet, called ex and written in the Latin script.
Used between the names of two characters to denote a ship, particularly in anime, manga, and video games.