Optical illusion and Pipe dream

Optical illusion noun - An optical phenomenon that results in a false or deceptive visual impression.

Pipe dream and optical illusion are semantically related. In some cases you can use "Pipe dream" instead a noun phrase "Optical illusion".

Pipe dream noun - A conception or image created by the imagination and having no objective reality.

Optical illusion and pipe dream are semantically related. Sometimes you can use "Optical illusion" instead a noun phrase "Pipe dream".