bubble under the radar
US /ˈbʌbəl ˈʌndər ðə ˈreɪdɑːr/
UK /ˈbʌbəl ˈʌndər ðə ˈreɪdɑːr/
1.
to be present or active but not widely known or noticed
:
•
The new startup has been bubbling under the radar for months, but now they're ready to launch.
•
Despite his talent, the artist has been bubbling under the radar, waiting for his big break.