Reflector

[Raeanne Dimick]

Something having a polished surface for reflecting light
or heat, as a mirror, a speculum, etc.

[Ernesto]

A piece of glass or metal for reflecting light in a required direction, e.g. a red one on the back of a motor vehicle or bicycle.

[Dianne]

A shiny red or [yellow light] that reflects off of a peice of plastic? (magical material) that helps cars and or [pedestrians] notice whats up. very helpful to [bicyclist] and one hell of an invention. props to the brilliant inventer. :

[Lizzy Liz]

an object on a bicycle, car, or other vehicle that reflects light and is intended to show the vehicles position to other road users