1. The act of getting the interest of another person, usually of the opposite gender, without putting thought into it before doing it, and capturing that person's attention. A function of an individual's personality.
2. What an individual is doing when he or she flirts without even knowing his or her actions are perceived as some type of flirt, whether it be simply making a wise crack for a smiling; or, with direct eye contact and raised eyebrows, a simple innocent flirt could be perceived as having a more romantic tone.
Either way, over time, it can lead to serious attraction.
He thinks he can't flirt and he completely misses that he is perceived that way by a majority of women with which he comes into contact each day. All he knows is that he makes wisecracks that get a laugh from the ladies and he loves an audience, the smaller the better. What he does is subconscious flirting, and he may be perceived as a persistent, non-stop, incessant flirt without intending to be.
Weeks, months, years or decades later, someone clues him in to the previously-existing or newly-found magnetic attraction.