from the GNU version of the Collaborative International Dictionary of English
- adj. 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.
Sorry, no etymologies found.