sonar

noun3

1. •
   Artificial echolocation by use of electronic equipment, with hydrophones to locate objects underwater, using the same wave-analysis principles that radar uses.

   • They were able to detect the sunken wreck using sonar.
2. •
   Any echolocation.

   • Submarines and bats both use sonar to navigate.
3. •
   A device that provides such echolocation.

   • They finally bought a new sonar to replace the 40-year-old unit that sometimes didn't work right.