| Acronym | Definition |
|---|
| X | 10 (Roman numeral) |
| X | Extra |
| X | Unknown Quantity (variable) |
| X | Experimental (US Military aircraft designation, as in X-1) |
| X | Telephone Extension |
| X | X Windows (TCP/IP-based network-oriented window system) |
| X | Multiplied by |
| X | MPAA Movie Rating for Adults Only |
| X | Special Equipment (Stores 100 code) |
| X | Generation X |
| X | X-ray (aviation letter code) |
| X | Cross |
| X | Ex (former) |
| X | Strike |
| X | Exchange |
| X | Kiss |
| X | Corporation (IRB) |
| X | Existing |
| X | Exercise |
| X | Except (medical orders) |
| X | Transfer (prefix) |
| X | Christ |
| X | Extreme (games) |
| X | Strike (bowling) |
| X | Malcolm X |
| X | Axis (ophthalmological-related) |
| X | Ecstasy |
| X | Halogen (organic chemistry) |
| X | Northwest Territories (postal code designation, Canada) |
| X | Brigade (Graphical Representation/Army) |
| X | X Chromosome (genetics) |
| X | Xenophobia |
| X | École Polytechnique (French famous university) |
| X | Xerox Corporation |
| X | Reactance |
| X | X Gene (X-Men) |
| X | Offensive team (sports/coaching) |
| X | Behind the Goal (Lacrosse) |
| X | Special Distribution (Air Force) |
| X | Personal Mark (or signature) |
| X | 50 Proof (Alcoholic Beverages) |
| X | Female Chromosome |
| X | Perpendicular to Orbit Plane |
| X | Initial Position Error (of casualty) |
| X | 8-12 GHz frequency band |
| X | Exophoria At Distance (ophthalmology) |
| X | Horizontal axis in Cartesian coordinate system |
| X | [not an acronym] Last name taken by some Nation of Islam members |