Noah Webster
Rover
RO'VER, noun
1. A wanderer; one who rambles about.
2. A fickle or inconstant person.
3. A robber or pirate; a freebooter. [So corsair is from Latin cursus, curro, to run.
At rovers, without any particular aim; at random; as shooting at rovers.
[I never heard this expression in the United States.]