忽上忽下
hū​shàng​hū​xià

to go up and down

忽上忽下 hū​shàng​hū​xià
to go up and down adverb
to move upwards and downwards rapidly; to flit about

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.

to feel anxious
to describe an unsettled or anxious feeling, like one's heart is jumping up and down
to fluctuate
to undergo sharp fluctuations; to rise and fall quickly (of prices, levels, or performance)