This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

n. Unreality.

n. the state of being insubstantial or imaginary; not existing objectively or in fact

"You may have had a similar experience—that sense of irreality and of focusing on the unimportant detail in the face of something hideous."

nonentity    nonexistence   

falseness    cloud    falsity