To reapply means to apply again, usually after a first attempt didn't work out or after something has worn off or expired.

You might need to reapply sunscreen after swimming because the water washed it away. Your older sister might reapply to a college that rejected her the first time, after improving her grades and test scores. When paint on a fence starts peeling, you reapply a fresh coat to protect the wood.

The word suggests a second (or third, or fourth) effort. Sometimes you reapply because the first application wore off or needs refreshing, like reapplying lip balm when your lips get dry again. Other times you reapply because you didn't succeed initially but want another chance, like reapplying for a competitive summer program after being waitlisted.

Notice that reapplying often takes patience and persistence. A job applicant might need to reapply multiple times before getting hired. A scientist whose grant application gets rejected might revise and reapply. The “re-” prefix tells you this is about trying again, often with improvements based on what you learned the first time.