A contrivance for permitting a body to incline freely in
   all directions, or for suspending anything, as a barometer, ship's
   compass, chronometer, etc., so that it will remain plumb, or level,
   when its support is tipped, as by the rolling of a ship. It consists of
   a ring in which the body can turn on an axis through a diameter of the
   ring, while the ring itself is so pivoted to its support that it can
   turn about a diameter at right angles to the first.