Bitternut is a term used to describe the fruit of a hickory tree. However, there are several synonyms for the word that can be used interchangeably depending on the context in which it is used. Some of the synonyms for the word bitternut include pignut, swamp hickory, water hickory, and yellow hickory. These terms are commonly used among botanists and agriculturists who specialize in identifying various species of trees and plants. Regardless of which synonym is used, all of them refer to the edible and nutritious nuts that are produced by the hickory tree.