vlf
/ˌviː ɛl ˈɛf/
noun
- Very low frequency; a radio frequency range from 3 to 30 kHz, used for long-distance communication and navigation.
- The submarine received signals on the VLF band while underwater.
- Scientists use VLF to study the Earth's ionosphere and lightning activity.
- VLF waves can travel long distances and penetrate deep into the ocean.