2. (Science: chemistry) Noting, or conforming to, that system of crystallization in which the three axes are of equal length and at right angles to each other; monometric; regular; cubic. Cf. Crystallization. Isometric lines, lines representing in a diagram the relations of pressure and temperature in a gas, when the volume remains constant. Isometrical perspective. See perspective. Isometrical projection, a species of orthographic projection, in which but a single plane of projection is used. It is so named from the fact that the projections of three equal lines, parallel respectively to three rectangular axes, are equal to one another. This kind of projection is principally used in delineating buildings or machinery, in which the principal lines are parallel to three rectangular axes, and the principal planes are parallel to three rectangular planes passing through the three axes.