UXO

Unexploded Explosive Ordnance Explosive ordnance which has been primed, fuzed, armed or otherwise prepared for action, and which has been dropped, fired, launched, projected, or placed in such a manner as to constitute a hazard to operations, installations, personnel or material and remains unexploded either by malfunction or design or for any other cause. ...

UXO

See unexploded explosive ordnance.
Found on http://www.aboutmilitaryschools.org/military/glossary/u.html

UXO

Unexploded Ordnance
Found on http://en.wikipedia.org/wiki/List_of_U.S._government_and_military_acronyms
No exact match found