Someone who stands in front of a show (as at a carnival) and gives a loud colorful sales talk to potential customers WordNet 3.0 & Open English WordNet

A barker, often a carnival barker, is a person who attempts to attract patrons to entertainment events, such as a circus or funfair, by exhorting passing members of the public, announcing attractions of the show, and emphasizing variety, novelty, beauty, or some other enticing feature of the show. Wikipedia

A person who attempts to attract patrons to entertainment events Wikipedia Disambiguation

Profession Wikidata

A person employed to solicit customers by calling out to passersby, e.g. at a carnival. Wiktionary

Person employed to solicit customers by calling out to passersby. Wiktionary (translation)