hēi​xiāng

black box

黑箱 hēi​xiāng
black box noun
a complex system or process whose internal workings are hidden or not understood, often used in computing or cybernetics
flight recorder noun
an electronic device used in aircraft to record technical data and cockpit conversations for accident investigation

Frequency

Written text
0.428 per million

Sources

Definitions
CC-CEDICT
Frequency data
BCC Corpus (BLCU)