†3.Mathematics. eversion of proportion: the principle that, given quantities A, B, C, and D, the proportionality of A to A−B is the same as that of C to C−D whenever that of A to B is the same as that of C to D. Obsolete. rare.
ΚΠ
1570 H. Billingsley tr. Euclid Elements Geom.v. f. 134 Conuersion of proportion (which of the elders is commonly called euerse proportion, or euersion of proportion [L. euersa proportionalitas]).