Is anything flat?

If the world is indeed round (and I'm not saying it is), how can we call anything "flat"?  Wouldn't anything we determine to be "flat" actually be rounded at the same arc as the curvature of the earth?

Also, if that is actually the case, then shouldn't anything that is indeed flat actually have a slight sonvex shape, forcing object to slide/roll toward the centre?

If the world is indeed round (and I'm not saying it is), how can we call anything "flat"?  Wouldn't anything we determine to be "flat" actually be rounded at the same arc as the curvature of the earth?

Well that would be a no.
Something is not considered 'flat' by comparison to the curvature of the earth.

Also, if that is actually the case, then shouldn't anything that is indeed flat actually have a slight sonvex shape, forcing object to slide/roll toward the centre?

And, The Earth is Freiken Huge You Idiot, So nothing is really big enough to bend with the earth. It is so large that it looks flat to your tiny eyeballs, or maybe it's the fact that you've never seen the earth because you are cooped up in your grandmas basement trying to pretend you have a life by claiming the earth is flat. 
 

And, The Earth is Freiken Huge You Idiot, So nothing is really big enough to bend with the earth. It is so large that it looks flat to your tiny eyeballs, or maybe it's the fact that you've never seen the earth because you are cooped up in your grandmas basement trying to pretend you have a life by claiming the earth is flat. 
 

Let's not be giant hateful douche-bags, you stupid piece of shit with boogers for brains eat a brick & die, ok?

If the earth is round, and the surface of a table is not, than gravity would have a great er effect at the point closest to the earth.  This would then mean that the center of the table is under a stronger pull, and objects, particularly round ones would have a tendency to move to this point.  In order for gravity to operate equally on all points of a table, or any other flat surface, it must be rounded to the same degree of the surface of the earth on which it is placed.

Also, if that is actually the case, then shouldn't anything that is indeed flat actually have a slight convex shape, forcing object to slide/roll toward the centre?

I shall answer with:

The Earth is Freiken Huge

Thus, any apparant convexity is actually miniscule, and is not noticed when other forces like friction are much more important in determining whether the object moves or not.