sporadic

Occurring at irregular intervals or in isolated or scattered places; having no pattern or order: synonym: periodic.

Separate; single; scattered; occurring singly, or apart from other things of the same kind; widely or irregularly scattered; of exceptional occurrence (in a given locality); straggling.

In phytogeography, distributed in several regions: so used specifically by A. P. de Candolle (French sporadique), in contrast with endemic, of plant genera whose species are thus distributed. Compare polydemic.

Occurring singly, or apart from other things of the same kind, or in scattered instances; separate; single

a disease which occurs in single and scattered cases. See the Note under Endemic, a.

Rare and scattered in occurrence.

Exhibiting random behavior; patternless.

recurring in scattered and irregular or unpredictable instances