Euclidean Subj. is a term used in geometry to refer to the study of Euclidean geometry, which is a type of geometry based on the work of the ancient Greek mathematician Euclid. The crossword solution for this term is GEOM, which is an abbreviation for geometry. Euclidean geometry is a branch of mathematics that deals with the properties of shapes and figures in two-dimensional space. It is used to solve problems related to angles, lines, circles, and other geometric objects.