Over filling is a term used to describe the state of something that has been filled beyond its capacity or limit. Some antonyms for over filling are under filling, emptying, removing, or clearing. Under filling implies that something has not been filled sufficiently, left incomplete, or requires more filling. Removing and clearing refer to the act of taking out or cleaning something that has been filled. In this case, there is no overfilling involved. So, if you want to avoid over filling, you can make sure to under fill, remove, or clear before filling again.