What is "at rovers"

Rover \Rov"er\, n. [D. roover a robber. See Rove, v. i.]

1. One who practices robbery on the seas; a pirate.

   Yet Pompey the Great deserveth honor more justly for scouring the seas, and taking from the rovers 846 sail of ships.
   --Holland.

2. One who wanders about by sea or land; a wanderer; a rambler.

3. Hence, a fickle, inconstant person.

4. (Croquet) A ball which has passed through all the hoops and would go out if it hit the stake but is continued in play; also, the player of such a ball.

5. (Archery)

   1. Casual marks at uncertain distances.
      --Encyc. Brit.

   2. A sort of arrow. [Obs.]

      All sorts, flights, rovers, and butt shafts.
      --B. Jonson.

      At rovers, at casual marks; hence, at random; as, shooting at rovers. See def. 5 (a) above.
      --Addison.

      Bound down on every side with many bands because it shall not run at rovers.
      --Robynson (More's Utopia).

prep.phr. (context obsolete English) At casual marks; hence, at random.