Does "Gibbet" = "Gallows"?

A gibbet is described on various websites as being a vertical pole (or what-not) with one arm on which corpses were hung on display, but some places also say that it could be used as an alternative form of "Gallows" (which would be the two vertical poles on the side with the horizontal one in between). My question is, would someone then be able to use the term "gibbet" in a story when they were describing gallows? For example, could they say gallows in one part and then, in order to not use the same word over and over, say something such as "drop the floor of the gibbet"? Or would it not convey the same image?