Adjective: Used to describe a thing, act or object that expresses and requires intimacy beyond what usually occurs in a relationship, highly subjective and eluding understanding outside of said relationship.
Noun: Used to refer to people that either are perceived to be able to be romantic more often than others or people that believe in some kind of scheme of live where idealized love has any meaning. Often used derogatory.
Alice: It was so romantic when Ted and I went catching psychotropic toads and smoked them in abandoned factories.
Alice: I think Bob is a romantic.
Carol: You'll never know until you try.