An interval, or time interval, was the measure of time required for a cycle to complete.
Old Faithful, a geyser found in Yellowstone National Park on Earth, was so called because of its regular eruption cycle occurring in semi-regular intervals. In 2365, Doctor Paul Stubbs compared the unusual neutron star/red giant binary system in the Kavis Alpha sector to Old Faithful because of the regular 196 year interval between expulsions of neutronium by the neutron star. (TNG: "Evolution")
On Ocampa, the homeworld of the Ocampa, the Caretaker provided the Ocampa with nutritional supplements, dispensed from their food processors every 4.1 intervals. (VOY: "Caretaker")
The term "interval" was used elsewhere in the episode, in describing the pulses of energy sent by the Caretaker's array to the Ocampa homeworld. Given that this energy sustained the Ocampa society, this might not be a coincidence.