I understand your position, but I am actually trying to explore the issue beyond the presented confines -- or actually by diving into the matter.
As for the "standard definition", it would render those married couples who cannot have sex for medical reasons "not actually married". I think the standard definition is, though accepted, an overemphasis on some aspects of the marital relationship (ie imbalanced).
My great aunt once said that she could not understand the new fangled idea of courtship and marriage. "In my day", she said, "we didn't have 'romance', instead we said let's raise a family together". Ie sex was not a central definition, but marriage was a life of shared effort, through which relationship developed, deepened and thrived. (She and my great uncle, like all of that generation in my family, lived out their married lives without divorce; they all had what seemed to me to have perfected that relationship to a "dance" beyond deep friendship, where each partner sensed, knew and stepped in to the center to create a seamless whole. Such beauty !)
Finally, I mentioned unceasing prayer as it has been said here that restraining from sexual activity for any reason other than prayer is beyond what is written; sinful.