"Imaginary line" refers to a line that does not physically exist but is used to represent or define a boundary, axis or trajectory. There are several synonyms for this term which could be used in different contexts. These include "fictitious line," "abstract line," "hypothetical line," "theoretical line," "virtual line," "invisible line," "conceptual line" and "ideal line." For example, the equator is an imaginary line that circles the Earth, dividing it into the Northern and Southern Hemispheres. Similarly, the Prime Meridian is another imaginary line that runs vertically from the North Pole to the South Pole, dividing the Earth into the Eastern and Western Hemispheres.