A person (usually an adult, not a child) who typifies or is the perfect example of a particular characteristic, attitude, opinion, cause, or type of person. Pete managed to disassemble their washing machine, fix the problem, and then reassemble it all by himself? Wow, he's like the poster child of DIY. Ms. Walsh built her fortune from nothing, through her own tireless work and intense ambition. She really is the poster child for the rags-to-riches American Dream.