What do you mean by overstay?
What do you mean by overstay? to stay longer in a place than you are allowed or wanted: Be careful not to overstay your visa. They left the party at 11 p.m., careful not to overstay their welcome.
What is the difference between stayover and overstay?
When you visit a place and find that by the end of the day, you have not finished what you came there for, you stay over. It could be at a hotel or a guest house or at someone's home. When you stay longer at a place than you were expected to, you are overstaying.