It refers to a certain type of revolver tool changer on CNC machining centres, in which the tools are arranged in a circle, facing outwards; thus, in a "star-shaped" manner and have their own motor. The change of the tools in the motors had to happen manually, because there was no tool interface yet.
Later, as tool holders like ISO30 or ISO40 were introduced to the market, the term revolver tool changer was used for changing systems, where the tool holders are embedded in the periphery of an upstanding, disc-shaped changer, so that the tools point outwards in the radial direction. This systems were available also with tool holders pointing outwards. Due to the star-shaped form this system was called "star-changer" (or rotational changer), but neither the system nor the term are used anymore.
With the launch of horizontally positioned disc tool changers the common revolver tool changer was nearly eliminated. Occasionally it is used equally to the term tool changing systems.
The manufacturers Bre.Ma. and Re.M are producing systems, which they call revolver tool changers to distance their systems from disc tool changers. These systems consist of a disc in an upright position with fixed aggregates. It is able to spin, so that the aggregate can be positioned in front of the drive screw.
During the 1990s the manufacturer Jonsdorf, that is not existent anymore, produced a system with fixed aggregates, too.