This illusion is of a shifting gestalt: sometimes a rabbit is seen, sometimes a duck.

My wife and my mother-in-law: Another famously ambiguous illusion

All is Vanity by Charles Allan Gilbert: It is a memento mori-themed painting, it actually depicts a woman gazing into a boudoir mirror, however, we have the illusion to see the perfect form of a human skull as well.

Ambiguity means that what a thing is, is not clear. Literally, the word refers to a choice between two different things. In the proper sense it should mean “two different meanings” because “ambi” comes from the Greek word for “two”.

We see things happen, and then we decide what they mean. If we cannot decide what is going on, the event is ambiguous. This is an extension of the original use of the word.