Time meters that can't be divided are called "indivisible" or "inseparable."
Time signatures that can't be divided are called what
Time signatures that can't be divided are called "irrational" or "unmeasurable."
Time units that cannot be further divided are called fundamental units or base units. In the International System of Units (SI), the fundamental unit for time is the second (s). The second is defined as the duration of 9,192,631,770 cycles of radiation corresponding to the transition between two energy levels of the cesium-133 atom.
