XYZ (?ks?w?-z??)interj. Informal Used to indicate to someone that the zipper of his or her pants is open.[ex(amine) y(our) z(ipper).]American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.