ˈposter ˌchild noun [countable usually singular] American English

1. a child with a particular illness or physical problem whose picture appears on a poster advertising the work of an organization that helps children with that problem

2. someone or something that represents a particular quality, idea etc – often used humorously:
Dillon is the poster child for wasted talent.

[TahlilGaran] Dictionary of Contemporary English ▲