Pink elephants and Visual hallucination

Pink elephants noun - Any visual hallucination arising from heavy drinking.

Visual hallucination and pink elephants are semantically related. In some cases you can use "Visual hallucination" instead a noun phrase "Pink elephants".

Visual hallucination noun - Illusory visual perception.

Pink elephants and visual hallucination are semantically related. Sometimes you can replace phrase "Pink elephants" with "Visual hallucination", this phrases are similar.