reflector

Short definition from Wiktionary

Noun

1. 1
   Something which reflects heat, light or sound, especially something having a reflecting surface.
2. 2
   A reflecting telescope.
3. 3
   A small, often red, reflecting disk on the rear of a vehicle or bicycle that reflects the headlights of other vehicles.
4. 4
   A safety reflector.
5. 5
   One who reflects on something; one who thinks or considers at length.
6. 6
   Something that is reflective (indicative) of something else.
7. 7
   A pattern which can change the direction and/or offset of an oncoming spaceship without being destroyed.