Many people flirt with others even when they are in a serious relationship. They believe that as long as they are not sexually involved with another person, it is not cheating. However if your flirting hurts your partner, maybe you should think twice.
Flirting takes on the mantle of cheating the moment the innocent and harmless smiles, teasing and winks lead to emotional infidelity. The moment you start dreaming of spending time with the other person rather than your partner, then flirting is emotional cheating.
It’s not a physical affair, they are emotional affairs. These affairs are equally harmful for a relationship like a physical affair. So, by default you are emotionally cheating on your partner and your flirting is cheating. If you continue on this path, you will end up ruining your relationship.