* Eisai (είσαι) means "you are" in Greek.
* Koukla (κούκλα) means "doll" in Greek.
Therefore, "eisai koukla" literally translates to "you are a doll".
It's important to note that this phrase would be unusual to hear in everyday Greek conversation. It could be used as a playful term of endearment, meaning "you are so cute/pretty," but it could also be interpreted as a strange or even insulting statement depending on the context.
Without more information about the situation in which you heard or encountered this phrase, it's impossible to give a definitive interpretation.