Sounder (noun)

1. An instrument used to measure the depth of water or to locate underwater obstacles.
2. A group of swine or hogs.
3. A device used to locate fish underwater in fishing.
4. An electrical device used to determine the depth of a borehole.

Origin:

Derived from the old english 'sundor' meaning to sound or probe.

Examples:

1. The captain used a sounder to navigate the shallow waters near the shore.
2. The farmer had a sounder of pigs on his farm.
3. The fisherman used a sounder to locate a school of fish below the surface.
4. The geologist used a sounder to determine the depth of the borehole.
5. The sounder beeped to indicate that the water was getting deeper, allowing the captain to adjust his course.