Subduplicate \Sub*du"pli*cate\, a. (Math.)
Expressed by the square root; -- said of ratios.
[1913 Webster]
{Subduplicate ratio}, the ratio of the square roots, or the
square root of a ratio; thus, the subduplicate ratio of a
to b is [root]a to [root]b, or [root]a/b.
[1913 Webster]