April Fool Definition

noun
The victim of a joke or trick played on April Fools' Day.
American Heritage
Victim of jokes played on April Fools' Day.
Webster's New World
The joke or trick so played.
American Heritage
A person subjected to a practical joke on April Fools' Day. Often used as an exclamation upon revealing the joke.
Wiktionary
A practical joke played on April Fools' Day.
Wiktionary
verb

To prank on April Fool's Day.

Wiktionary