1 sentence for 忽 (hū — alternating)

1. 有一只蝴蝶正在花丛里忽上忽下地飞着。

   yǒu yī zhī hú​dié zhèng​zài huā​cóng li hū​shàng​hū​xià de fēi zhe.

   A butterfly is flying up and down among the flowers.

   Source: UM-Corpus: Spoken