YAY Meaning of YAY in English [ jeɪ ](also yea ) ■ adverb N. Amer. informal1》 (with measurements) so; to this extent: I knew him when he was ~ big.2》 to a considerable degree; much.Origin1960s: prob. a var. of yea . Concise Oxford English vocab. Сжатый оксфордский словарь английского языка. 2004