Longman Dictionary of Contemporary English
Wiktionary
n. (context idiomatic English) One who is a prototypical or quintessential example of something.
WordNet
n. a child afflicted by some disease or deformity whose picture is used on posters to raise money for charitable purposes; "she was the poster child for muscular dystrophy"
Wikipedia
The term poster child (sometimes poster boy or poster girl) originally referred to a child afflicted by some disease or deformity whose picture is used on posters or other media as part of a campaign to raise money or enlist volunteers for a cause or organization. Such campaigns may be part of an annual effort or event, and may include the name and age of a specific child along with other personally identifiable attributes.
The definition of "poster child" has since been expanded to a person of any age whose attributes or behaviour are emblematic of a known cause, movement, circumstance or ideal. Under this usage, the person in question is labeled as an embodiment or archetype. This signifies that the very identity of the subject is synonymous with the associated ideal; or otherwise representative of its most favorable or least favorable aspects.
Usage examples of "poster child".
And the poor kid ends up being a poster child for the La Salle Heights project in action.
Gwynnie was beginning to seem less and less the poster child for teen angel.
It had been a national best-seller about four years ago, when I'd thought I knew the meaning of my life, prior to my discovery that my mother, out of fierce maternal love and a desire to free me from my disability, had inadvertently made me the poster child for doomsday.
It had been a national best-seller about four years ago, when I'd thought I knew the meaning of my life, prior to my discovery that my mother, out of fierce maternal love f and a desire to free me from my disability, had inadvertently made me the poster child for doomsday.
Then he needed half a minute to recognize Satranji's proclaimed wife, the robot Dorijen, who was standing before him in the role of a poster child for the problem of collateral damage.
Ruth May usually fell asleep, open-mouthed in the heat, with her hair plastered down across her sweaty face like the poster child for fever.