In this case, it definitely isn’t, and I doubt you’d be asking unless you really already had an idea that it was. I can see it being ok between two single people (ie, people not in relationships of any kind, not just unmarried), but you admittedly have a significant other, and all I can guess is that if people know that, and you’re seen flirting around with women at work, then she really doesn’t seem all that significant to you at all (and it makes you look like a royal douche).
It might seem playful and harmless, but it rarely stays that way. Are you planning on telling your S/O about your adventures in flirtation at the workplace? Don’t flirt… If you feel the need to, then that might be a sign that your relationship really isn’t working.