What does it mean two vectors reciprocally perpendicular?

Question

If I have two vectors $\vec a$=(x,y,z) and $\vec b$=($x_1$,$y_1$,$z_1$) by reciprocally perpendicular does it mean ($\frac1x$,$\frac1y$,$\frac1z$) * ($\frac1x_1$,$\frac1y_1$,$\frac1z_1$) = 0 ?

Answer 1

I've never encoutered this definition, maybe it is a rendundant mode to simply say that they are $mutually$ perpendicular, that is obvious since orthogonality for vectors is a reflexive property.