There are a few synonyms that can be used for the term "Lewis and Clark Expedition." One such synonym is the "Corps of Discovery," which refers to the group of individuals assembled by Meriwether Lewis and William Clark to explore the western part of the United States in the early 1800s. Another synonym is the "Lewis and Clark Expedition of the American West," which accurately describes the geographical location of their journey. Additionally, the "Exploration of the Missouri River and Beyond" is another way to describe the expedition, as much of their journey focused on following and mapping the Missouri River. Ultimately, the Lewis and Clark Expedition is a significant moment in American history and has many ways of being referred to.