Introduced by René Descartes in the context of mathematical notation, but has since widened to other contexts.
Meanings
An unknown quantity or unknown value.
Let X represent the forecast traffic flow in 20 years’ time.
To know whether a word X is heterological, we must already know what X means. (By contrast, I can know that the word “subdermatoglyphic” has certain syntactic properties—it is six-syllabled, contains the letter “m”, etc.— without having any idea of its meaning.) This indirectness is fine as long as X already has an assigned meaning, for in that case the meaning of “heterological” is ultimately grounded. But when X is the word “heterological”, then we are trying to define “heterological” in terms of itself. We have a closed circle, and a contradictory one, due to the negation operator in the definition. 2020 January 30, Richard Johns, “Why Physicalism Seems to Be (and Is) Incompatible with Intentionality”, in Acta Analytica, →DOI, archived from the original on 10 Jul 2025, pages 7-8:
fi tuntematon (unknown quantity or unknown value) · mk икс (unknown quantity or unknown value) · de x (unknown quantity or unknown value) · ru X (unknown quantity or unknown value) · sv X (unknown quantity or unknown value) · fr X (unknown quantity or unknown value) · ar س (unknown quantity or unknown value) · mk X (unknown quantity or unknown value) · ru икс (unknown quantity or unknown value) · fi X (unknown quantity or unknown value)
Introduced by René Descartes in the context of mathematical notation, but has since widened to other contexts.
Meanings
A placeholder for an unknown, suppressed or hypothetical name.
Suppose that Mr and Mrs X have been married for many years.
The woman known until now as Witness X has been unmasked after a court ruling.
Although the Take Care Clause grants the president significant authority to enforce the laws, the duty to take care does not include a power to forbid the execution of the laws. Consequently, the president does not have the authority to disregard Congress’s declaration of war against Country X. On the contrary, the president has an obligation to faithfully execute the declaration of war, even against their own beliefs and wishes. 2023 November, Andrea L. R. Pillai, “Hawks and Doves: Evaluating Presidential Powers and Duties Against Congress's Power to Declare War”, in Duke Law Journal, volume 73, number 2, →ISSN, →OCLC, archived from the original on 11 Mar 2024, page 419:
A surname, used by those who have had their identity or heritage, including their proper ancestral names, erased or forgotten.
Malcolm X
(qualifier:social media) An online social media network, formerly known as Twitter.
Two senior USAid security officials were suspended on Sunday for blocking Doge officials from a restricted area, a day after the agency’s website went offline, and Musk posted to X that USAid was “beyond repair” and needed to be shut down. 2025 February 3, Richard Luscombe, “Marco Rubio appoints himself head of USAid as workers locked out of office”, in The Guardian, →ISSN, archived from the original on 04 Apr 2025:
(not-comparable) Intersex or non-binary (in passports and identification documents).
So last summer, when the Massachusetts State Legislature became one of the first in the nation to consider a bill to add an “X” option for nonbinary genders to the “M” and “F” on the state driver’s license, El, 17, was less surprised than some at the maneuver that effectively killed it. 2019 May 29, Amy Harmon, “Which Box Do You Check? Some States Are Offering a Nonbinary Option”, in The New York Times, archived from the original on 08 Jun 2019:
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.
The spot behind the goal.
Deriveds
xoxo (signature mark) · X marks the spot (cross mark) · X out (cross mark) · XOXO (signature mark) · XXX (cross mark) · xo (signature mark) · XO (signature mark)
Presumably by abbreviation of the pronunciation of ecstasy.
Meanings
(slang, uncountable) Ecstasy, a particular street drug.
I'm a love druggie falling for these drug junkies. Come n call on me besides these X parties. It's fucking hard on my body. 2018 June 8, “Love Druggie”performed by Mendoza:
You can find me in the club, bottle full of bub'. Look, mami, I got the X if you into takin' drugs. 2003 January 7, “In da Club” (track 5), in Get Rich or Die Tryin', performed by 50 Cent:
Tonight the kids will go out and party down in a more righteous mode. Alcohol and not a few tabs of X will be ingested. Club music will throb through big speakers. 2008, Stephen King, Graduation Weekend:
Translations (4)
fi eve (slang: ecstasy) · fi E (slang: ecstasy) · fi essi (slang: ecstasy) · fi xtc (slang: ecstasy)
If you go to an X movie you do so knowingly, as does everyone else in the audience. Or if the same thing comes up on TV you can switch over, or, if you wish, enjoy it in relative privacy. 1976, Movie Maker, volume 10, numbers 1-6, page 364: