Chicken Little Definition

noun

A confirmed pessimist, particularly one who warns of impending disaster.

American Heritage

A person who spreads baseless or exaggerated reports of danger; alarmist.

Webster's New World

pronoun

A children’s fable about a hen who, in the classical version, believes the sky is falling after an acorn hits her head, journeys to inform the King, and is finally eaten by Foxy Loxy. Also known by other names including The Sky is Falling.

Wiktionary

The main character in this story, a hysterical hen, alternatively named Chicken Licken under a different title.

Wiktionary

By extension, one who panics at the slightest provocation.

Wiktionary

Origin of Chicken Little

After a character in a story who is hit on the head by an acorn and believes the sky is falling

From American Heritage Dictionary of the English Language, 5th Edition