Definitions for "Unexploded Ordnance"
Explosive ordnance which has been primed, fuzed, armed or otherwise prepared for use or used. It could have been fired, dropped, launched, projected yet remains unexploded either through malfunction or design or for any other cause.
Explosive ordnance that has been primed, fuzed, armed, or otherwise prepared for action, and that has been fired, dropped, 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. Reference: DoD 6055.9 STD
Explosive ordnance that has been primed, fuzed, armed, or otherwise prepared for use and used in an armed conflict. It may have been fired, dropped, launched, or projected and should have exploded but failed to do so.