The term "level line" is often used to describe a straight, even line that runs horizontally. However, there are many synonyms that can be used to describe this type of line. Some possible synonyms include "horizontal line," "even line," "flat line," "straight line," "parallel line," and "level plane." These terms all describe a line that is straight and even horizontally. Other possible synonyms might include phrases like "perfectly flat" or "completely level." Ultimately, the term used to describe a level line will depend on the context in which it is being used, as well as the specific qualities of the line itself.