subtertius

A New Latin Dictionary by Charlton T. Lewis Ph.D. and Charles Short, LL. D.

sub-tertĭus, a, um, adj., of a number,

less by a third of itself (i. e. that bears to another the ratio of 3 to 4), a transl. of the Gr. ὑπότριτος: numerus, Mart. Cap. 7, § 761.