What is the adjective form of reminisce?

There isn't a single, commonly used adjective form of "reminisce."

However, you can use these options depending on the context:

* Reminiscent: This is the most common adjective form. It means "tending to remind one of something," or "evoking memories." For example, "The old photograph was reminiscent of her childhood."

* Recollective: This is a less common but still acceptable adjective that means "relating to or involving the act of remembering." For example, "He had strong recollective abilities."

You could also use phrases like "filled with reminiscence," "evoking memories," or "bringing back memories" to describe something that is reminiscent.