Top edge refers to the uppermost part of an object or surface. There are various synonyms that can be used to describe the top edge. One synonym is 'upper boundary' which refers to the upper limit or edge of something. 'Crown' is another synonym that can be used to describe the top edge, particularly when referring to the topmost part of a hill or landscape. The term 'crest' can also be used to describe the top edge, particularly when referring to the highest point of a wave or the upper part of a roof. Lastly, 'rim' is another synonym that can be used to describe the top edge, particularly when referring to the uppermost part of a container or bowl.