Is taking a puff from someone's cigarette considered flirting?

It can be the begining of flirting if you want it to be. Especially if its taking a drag off their cigarette that they were smoking, and then giving it back to them.

But if you want to make it more distant from flirting, you can just ask them for a cigarette. Again, it can be the begining of a pickup, if thats what you're aiming for; but it could just as easily be a way to make a new friend by breaking the ice and borrowing a cigarette.

Borriwing a cigarette, particularly when you accept a light from someone, can in fact be a great way to get a flirtatious conversation started. But the cigarette itself is not a complete flirt, its more of just an open invitation to either visit about that, or something else, or nothing at all, depending on your mood. A cigarette is not an obligation to flirt with someone any more than it is an obligation to go on a date with someone.

It's not only considered flirting, but highly sexual flirting. It involves your mouth on something someone elses mouth has been on, so it's like kissing. If you want just a puff of a cigarette, light one, take a puff and then put it out.

I wouldn't consider it flirting.

Don't worry it's not flirting at all!!