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.
Cross, crossing.
The spot behind the goal.
Ecstasy, a particular street drug.
Obscene.
Intersex or non-binary (in passports and identification documents).
The twenty-fourth letter of the English alphabet, called ex and written in the Latin script.
A surname, used by those who have had their identity or heritage, including their proper ancestral names, erased or forgotten.
Christ
A placeholder for an unknown, suppressed or hypothetical name.
An unknown quantity or unknown value.
One will find what one is looking for under an obvious sign for it.