yay
exclamation informal uk/jeɪ/ us/jeɪ/
（表示喜悦）好，耶，好耶
used to show that you are very pleased about something
"We won." "Yay!" “我们赢了。”“好耶！”
yay
adverb informal uk/jeɪ/ us/jeɪ/
informal这么，那么；十分，非常
so; to a particular degree
It was about yay long. 那个大约这么长。