Diesis

·noun The mark /;

— called also double dagger.

II. Diesis ·noun A small interval, less than any in actual practice, but used in the mathematical calculation of intervals.

diesis
dĭĕsis, is, f., = δίεσις. In ancient music, I A quarter-tone , Vitr. 5, 4; Macr. Somn. Scip. 2, ...

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