Depends on the context. If I’m thinking about poetry or philosophy (which I often am,) then it pertains to the early nineteenth century movement that counterpoised the Enlightenment. Those “Romantics” disliked what they saw as the cold rationality of Enlightenment thinking; they valued spiritual and mystical experiences, and they believed it was important to not throw out the spiritual “baby” with the bathwater. That is, like many Enlightenment thinkers, they realized that it was necessary to jettison many of religion’s noxious ideas (e.g. the concept of “chosen people”) and also realized that mindlessly following moral dictates that may or may not have made sense in the pre-Christian Levant could be detrimental to their present-day life experience. However, unlike most Enlightenment thinkers, they did find value in spiritual views of the world as well as in the pursuit of mystical experiences. William Blake (even though he is often labeled pre-Romantic) provides an excellent example. His poems are spiritual to the core, and yet explicitly reject a lot of the moralizing and toxic aspects of conventional religion.
Of course, that variety of “Romantic” is usually given a big-R, and so I suspect the question is after a more colloquial definition. With that in mind, I believe “romantic” means “that which facilitates the unity of two (or more, I don’t judge) people in an immersive intimate experience of each other during a common period of time.” I’m not big on trappings. I think people obsess over trappings because it allows them to slack on the physical / cognitive demands of being fully engaged. This is why sex (done well) is such a great tool both for relationship building and for personal development. It makes it relatively easy (i.e. rewarding) to stay fully engaged in a common experience and in the moment, and to not fall into the attentional abyss.
