Wiktionary
n. A retroreflective device or surface.
Wikipedia
A retroreflector (sometimes called a retroflector or cataphote) is a device or surface that reflects light back to its source with a minimum of scattering. In a retroreflector an electromagnetic wavefront is reflected back along a vector that is parallel to but opposite in direction from the wave's source. The angle of incidence at which the device or surface reflects light in this way is greater than zero, unlike a planar mirror, which does this only if the mirror is exactly perpendicular to the wave front, having a zero angle of incidence.
Usage examples of "retroreflector".
The arrangement is a retroreflector (like the one Apollo astronauts left on the Moon).
That was when the ship's laser ranging retroreflector first noticed that it was being hit by coherent light and locked in on the laser beam from the Moon transmitter.