Definition of "Mx"
Mx1
noun
(LGBT) A gender-neutral title used instead of Mr (Mister), Mrs (Mistress), etc.
Quotations
“I think the thing that was most surprising was how supportive and gung-ho a lot older alums were,” said Mx. LoSchiavo, who graduated this year (and would have been admitted under the new policy, having identified as a female at the time of application).
2015 June 4, Elizabeth A. Harris, “Barnard College, After Much Discussion, Decides to Accept Transgender Women”, in The New York Times
In the new Notice, the Court is asking people to state their name, title (sometimes called "salutation"), and pronouns to be used in the proceeding, and for lawyers to provide this information for their clients. For example: "My name is Ms. Jane Lee, spelled L-E-E. I use she/her pronouns. I am the lawyer for Mx. Joe Carter who uses they/them pronouns." ("Mx." is pronounced like the word "mix" and is a gender-neutral title/salutation.)
2020, Provincial Court of British Columbia, "A change in how parties and lawyers should introduce themselves in court," 16 December 2020
Mx2
noun
uncountable
(medicine) Abbreviation of management.