浮想聯翩

to let one's imagination roam

to float / superficial / floating / unstable / movable / provisional / temporary / transient / impetuous / hollow / inflated / to exceed / superfluous / excessive / surplus

passing thought / an idea that comes into one's head / recollection

to think / to believe / to suppose / to wish / to want / to miss (feel wistful about the absence of sb or sth)

to think (about) / to think of; to devise / to think (that); to believe (that) / to desire; to want (to) / to miss (feel wistful about the absence of)

to ally / to unite / to join / (poetry) antithetical couplet

(literary) to come in quick succession / wave after wave

to fly fast