radarra·dar /ˈreɪdɑ-dɑːr/ noun [uncountableU]1be off/below the radar (screen) used when saying that people do not know about or are not thinking about something, especially something that will later become importantMany of these technologies were below the radar of the mainstream business press.
HIV/AIDS has fallen off our radar screens in recent years.
2be on the radar (screen) used when saying that people know about or are thinking about something, especially something that will later become importantStem cell research and biotech in general are on the radar screen of venture capitalists nationwide.