彼は煩忙な日々を過ごしていて、休みを取る暇もない。
He is leading such a hectic life that he has no time to take a day off.
年末は業務が煩忙を極める。
At the end of the year, work becomes extremely busy.
煩忙のため、お返事が遅れましたことをお詫び申し上げます。
I apologize for my late reply, which was due to pressure of business.
煩忙な仕事の合間を縫って、彼女は小説を書き続けた。
She kept writing her novel in the gaps between her hectic work.