The term X OR Y can be solved by the crossword solution AXIS, which is a four-letter word. An AXIS is a straight line about which a body or geometric object rotates. In mathematics, an AXIS can refer to the x-AXIS and y-AXIS of a two-dimensional graph, which are used to plot points and lines. In physics, an AXIS can refer to the three axes of rotation in three-dimensional space. In biology, an AXIS can refer to the longitudinal AXIS of a plant or animal.