head over heels的字面意思是“头朝下，颠倒”，be head over heels in love with 坠入爱河，爱得神魂颠倒

【例句】
He is head over heels in love with that girl.
他深深地爱恋着那位姑娘。

Many girls are head over heels in love with Mike.
许多女孩子神魂颠倒地爱上迈克。