The correct spelling of the word is "most prolific," which means the highest producing or most fruitful. The incorrect spelling "wast prolific" may have come from confusion with the archaic form of "was" or "were," which is "wast" (pronounced /wɑːst/). However, the correct form of the adjective "prolific" is spelled with the suffix "-est" to indicate the superlative form. The correct pronunciation is /ˌmoʊst prəˈlɪfɪk/. Always double-check your spelling to avoid errors like this.