qīn​mì​wú​jiàn

intimate

亲密无间 (親密無間) qīn​mì​wú​jiàn
intimate expression
to have a very close relationship with each other

The two of them have been together since childhood and are extremely close.

Frequency

Movie subtitles
1.46 per million appears in 1% of films
Written text
1.02 per million

Sources

Definitions
CC-CEDICT