If "reapply" means to apply again:
* Withdraw: To take back an application.
* Decline: To refuse to apply.
* Forgo: To choose not to apply.
If "reapply" means to apply again for the same thing:
* Discontinue: To stop applying for something.
* Abandon: To give up on applying for something.
* Withdraw: To take back an application.
If "reapply" means to apply again for a different thing:
* Switch: To apply for something else.
* Divert: To direct one's application to something else.
* Change: To make a different application.
The best opposite will depend on the specific situation and what you are trying to communicate.