subcontrary

1. Contrary in an inferior degree.
   1. not comparablegeometryHaving, or being in, a contrary order; said of a section of an oblique cone having a circular base made by a plane not parallel to the base, but so inclined to the axis that the section is a circle; applied also to two similar triangles when so placed as to have a common angle at the vertex, the opposite sides not being parallel.

      Two planes drawn through the vertex of the cone parallel to the plane of the circular base , and that of a subcontrary section, are called by Chasles the cyclic planes of the cone

      1852, John Mulcahy, Principles of Modern Geometry

   2. not comparablehuman sciencesDenoting the relation of opposition between the particular affirmative and particular negative. Of these both may be true and only one can be false.

plural subcontraries

1. human sciencesEither of a pair of propositions at least one of which must be true