Beaver (noun)

1. A large rodent found in North America and Europe that builds dams and lodges in streams, rivers, and lakes.
2. A person who works with great diligence and energy.

Origin:

From the old english word "befer".

Examples:

1. The beaver built a dam across the stream.
2. The beaver's lodge could be seen from the river.
3. The beaver's fur was highly valued for its warmth.
4. He was a real beaver when it came to his work.
5. The beaver's teeth were constantly growing.