I would argue that a good analogy holds between the use of the word in math, and in ordinary discourse. If two phenomena related to a given field of discourse have effects that can reasonably taken to be independent of each other, than it's reasonable to call them othogonal, even if they haven't an exact metric you can use measuring instruments on. As in, for instance, the claim of a mother that her love for her child does not diminish her love for her husband. Orthogonal love--I've got pictures from the Kama Sutra.