Sesquiduplicate \Ses`qui*du"pli*cate\, a. [Sesqui- + duplicate.]
Twice and a half as great (as another thing); having the
ratio of two and a half to one.
[1913 Webster]
{Sesquiduplicate ratio} (Math.), the ratio of two and a half
to one, or one in which the greater term contains the
lesser twice and a half, as that of 50 to 20.
[1913 Webster]