Stasis is short for 'GastroIntestinal Stasis', it's when the rabbits gut shuts down and it can be fatal
The most common signs are rabbits refusing food, sitting hunched in a corner, loud noisey gut or silent gut, grinding teeth etc.
I believe you should always (whenever possible) take the rabbit straight to a vet to have it checked for blockages and treated with pain relief (metacam)and possibly gut stimulants (metoclopramide)
If you don't know about stasis, I strong recommend you do some research online, it can mean saving your buns life, should it go into stasis.