頻しく

yodan verb with 'ku' ending (archaic), intransitive verb

occur repeatedly; be repeated

Archaic intransitive yodan verb meaning that something happens again and again. In modern Japanese, this meaning is usually expressed by 繰り返される or 頻発する.

• 古こ語ごでは「雨あめが頻しく」のように、同おなじことが繰くり返かえし起おこることを表あらわした。

  In classical Japanese, 頻く was used to express that something like rain occurs repeatedly.