retrodirective

/re-troh-di-rek-tiv, -dahy-/US // ˌrɛ troʊ dɪˈrɛk tɪv, -daɪ- //

复古的指令,复古指令,复古指示,复古指导

Definitions

adj.形容词 adjective

1
Optics.
- : having three reflecting surfaces so oriented that a ray of light is reflected in a direction parallel but opposite to its original direction.