have a crush on的意思是指“爱上了……，对……有好感，喜欢上了……”

英文解释：
to have a feeling of romantic love for someone, especially someone you do not know well.

When you have a crush on someone, you like that person. You usually feel uneasy and try to get attencion around that person. Sometimes, it's hard to stop thinking about them.

例句：
Do you still have a crush on Jessica?
你还喜欢着杰西卡吗？

Sometimes the kids think they fall in love when they have a crush on someone else in the class, when they're eight or ten years old or something like that.
八岁或十岁左右的孩子有时会迷恋班上某个人，然后就以为自己恋爱了。

You friend Jack Turner seems to have a crush on Susan Tompkins.
你的朋友杰克·特纳好像迷恋上了苏珊·汤普金斯。