The term “narcissism” was only coined at the close of the nineteenth century, to refer to pathological self absorption, egotism, or sexual attraction to oneself over others.

In current usage, it refers to a self–centered personality style characterized as having an excessive preoccupation with oneself and one's own needs, often at the expense of others, which fits Trump like a particularly small glove.

Sure, it's named after Narcissus, from Graeco-Roman mythology, who is indeed said to have rejected everyone's sexual (and romantic) approaches (guy was so mythically attractive that everyone fell for him)... but, according to most versions of the myth (including the ones that inspired the term), he was very much capable of sexual and romantic attraction... to himself, to the point that, being unable to properly fuck himself as he wanted to, he took his own life in frustration.