At an occasional, infrequent, or irregular frequency

(archaic) (of diseases) occurring in isolated instances; not epidemic. / Rare and scattered in occurrence. / Exhibiting random behavior; patternless.

An archipelago in the Aegean Sea.

sporadic.

(astronomy) Stars not included in any constellation.

The quality of being sporadic.

(radio) A meteorological phenomenon where radio waves above a certain frequency are reflected in the atmospheric E region, allowing these radio waves to be received in distances up to 1,200 miles.

(group theory) Any one of the 26 exceptional finite simple groups, which do not belong to any of the general, infinite categories specified by the classification theorem for finite simple groups.

plural of sporadic group