I can't really think of how I'd word my definition of flirting, but for me it's either
A) To show you're interested in someone
B) To enhance romantic chemistry
C) If someone's willing to flirt with you, it must mean they value you as at least someone they could relate to and trust, not just another random acquaintance.
D) Basically just to have a laugh and to entertain each other really.
But different people have different personality.
As I said I don't think I'd be able to provide a coherent definition, but I have an idea of it in my head, and to be honest I don't think about what It means, when you flirt you just know it's happening.
Flirt definition from OED;
Flirt: [verb] behave as though sexually attracted to someone, but playfully rather than with serious intentions
Nicely put.
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