xīn yuán yì mǎ

ㄒㄧㄣㄩㄢˊ ㄧˋ ㄇㄚˇ

Idiom

1to have ants in one's pants

2hyperactive

3adventurous and uncontrollable

4lit. heart like a frisky monkey, mind like a cantering horse (idiom); fig. capricious (derog.)