under-the-radar

US /ˈʌndər ðə ˈreɪdɑːr/
UK /ˈʌndər ðə ˈreɪdɑːr/
"under-the-radar" picture
1.

不為人知, 低調, 秘密的

not attracting much attention; unnoticed or secret

:
The small, independent film was an under-the-radar hit.
這部小型獨立電影是一部不為人知的佳作。
They prefer to keep their relationship under-the-radar.
他們更喜歡讓他們的關係不為人知