The word "Niobrara" is a noun that refers to a specific river in the United States. It is a tributary of the Missouri River, which means that it flows into the Missouri River. The Niobrara River is located primarily in the state of Nebraska and is known for its scenic beauty and recreational opportunities.
In more advanced discussions, you might talk about the environmental significance of the Niobrara River or its historical importance to Native American tribes and early settlers.
Since "Niobrara" is a proper noun (the name of a specific river), it does not have direct synonyms like common nouns do. However, you could refer to it as a "river" or a "waterway" in a general sense.
There are no specific idioms or phrasal verbs that include the word "Niobrara" since it is a proper noun. However, you could use general phrases related to rivers, such as "flowing like a river" to describe something that is smooth and continuous.
In summary, "Niobrara" is the name of a river in the U.S. that flows into the Missouri River.