(someone) has plans for (a time)

"Having plans" means that you've made an appointment or a decision to do something at a certain time. You can ask someone whether they "have plans":

Do you have any plans for Saturday?

Do you have plans for later this afternoon?

You can also refuse someone's invitation by saying that you "have plans":

A: Why don't we go grab a coffee?

B: Sorry, but I actually have plans.

This phrase appears in these lessons: