Spasiba in Russian means thank you.
In Cyrillic it’s written спаси́бо.
Spasiba is a very important and must know word in Russian. If you want to give a good impression about yourself, use it as often as the situation allows.
If you want to say thank you very much, it will be большо́е спаси́бо [bal’-shó-ye spa-sée-ba] (which literally means big thank you).
A more informal way (in the style of “okie” instead of “okey”) would be spasibachki:
Keep in mind that it is only suitable between friends and relatives, otherwise it sounds not adequate.
Also pay attention, that spasiba in Russian is spelled with the last O but pronounced with A. You can learn more about Russian pronunciation here.