| Term |
Definition |
| Objective Lens |
The objective lens is the lens closest to the object being viewed. |
| Ocular Lens |
The ocular lens is the lens closest to your eye. |
| Out of Battery |
It refers to the status of a gun before the action has returned to the normal firing position. |
| Over Under (OU) |
A double barrel gun where one barrel is positioned on top of the other. |