What is "x mark"

n. A symbol comprised of two perpendicular lines (✗), especially when representing negation or lack of verification.

An x mark (also known as a cross, x, ex, exmark or into mark) is a mark (x, ×, X, ✕, ☓, ✖, ✗, ✘, etc.) used to indicate the concept of negation (for example "no, this has not been verified" or "no, I don't agree") as well as an indicator (for example in election ballot papers or in x marks the spot). Its opposite is often considered to be the check mark or tick (or the O mark used in Japan, Korea and Taiwan). In Japanese, the X mark is called "batsu" and can be expressed by someone by crossing their arms. In some areas it's common for people to check a square box with a cross rather than a check mark, while in others the check mark or even a v mark is used.

It is also used as a replacement for a signature for a person who is blind or illiterate and thus cannot write his or her name. Typically, the writing of an X used for this purpose must be witnessed to be valid.

As a verb, to '''ex '''(or x, notably one of the shortest English words) off/out or to cross off/out means to add such a mark. It is quite common, especially on printed forms and document, for there to be squares in which to place x marks, or interchangeably checks.

It is also traditionally used on maps to indicate locations, most famously on treasure maps.