Being extremely busy; having many tasks or commitments and little free time.
多忙のため、返信が遅れて申し訳ありません。
Sorry for the late reply; I've been very busy.
年度末は多忙を極める。
The end of the fiscal year is extremely busy.
彼は仕事で多忙なので、週末しか会えない。
He's busy with work, so we can only meet on weekends.