IPA: /ˌeɪpəˈrɪdɪkli/
KK: /ˌeɪpəˈriːədɪkli/
In a manner that does not occur at regular intervals or times.
The events were scheduled aperiodically, making it hard to predict when they would happen next.
Aperiodically → It is formed from "a-" (meaning not) and "periodicus" (from Greek "periodos", meaning a cycle or recurring interval) and "-ly" (meaning in a manner). The word "aperiodically" means not occurring at regular intervals or cycles.
Think of 'not' ('a-') happening in a 'cycle' ('periodos') — that's why aperiodically means something that does not happen regularly.