Bhai exams paas aarahe hai meri gaand fat rahi hai !! (Trans:Bro exams are near it is scaring the shit out of me !!)
Mai teri gaand faar ke rakh dunga(I will tear your ass)
mai teri gaand maar dunga(I will f*ck you)
It is a body organ just beside your waist, or simply a butt hole.
Sometimes also used as phrases like, "Gaand phad dunga" which means will do something big and unexpected.