spiritual but not religious

[Belacqua]

Is it possible to be spiritual but not religious, 

Yes, why not!?

It's a bit fuzzy definition-wise, but there are times in life when uncertainty is the right choice. Hurrying to label yourself one thing or another might only shut down your options. 

You can have the great pleasure of working out, in your own life, what form this spirituality takes. Through action, through love, through the arts, etc. There's a great richness to be had. 

and if so could someone still be considered an atheist?

If you want to be. But it's just a label.