na-adjective
simultaneous and multiple; happening at the same time in different places
Describes events that occur concurrently in multiple locations. Often used in news contexts, e.g., 同時多発テロ (simultaneous terrorist attacks).
同時多発的な自然災害への備えが必要だ。
We need to prepare for simultaneous natural disasters.
同時多発的なサイバー攻撃が報告された。
Simultaneous cyberattacks were reported.
Compound of 同時 (simultaneous) + 多発 (multiple occurrences) + adjectival suffix 的.