Identify the misspelt word

The correct answer is Sacrilegous.

Let's analyze the spelling of each given option to identify the misspelt word:

1. Vicereine: Correctly spelled. It refers to a woman who rules a country or province as the representative of the monarch.
2. Floccinaucinihilipilification: Correctly spelled. It is a noun that means the action or habit of estimating something as worthless.
3. Defenestrate: Correctly spelled. It means to throw someone or something out of a window.
4. Sacrilegous: Incorrectly spelled. The correct spelling is Sacrilegious (with an 'i' after 'g'). It means committing or characterized by sacrilege; sacrilegious behavior or treatment of something sacred.

Therefore, the misspelt word among the options is Sacrilegous.