What is the greek word for slay?

There isn't a single perfect Greek word that translates to the modern slang meaning of "slay" (to impress greatly, to do something exceptionally well). The meaning is too nuanced. You'd need to choose a word based on the specific context. Possible options, depending on the nuance you want to convey, include:

* νικάω (nikáō): This means "to conquer," "to win," or "to overcome." This works if "slay" implies triumph or excellence in competition.

* υπερβαίνω (hyperbaínō): This means "to surpass," "to exceed," or "to transcend." This is suitable if "slay" refers to exceeding expectations.

* θαυμάζω (thaumazō): This means "to admire," "to marvel at," or "to wonder at." This would be appropriate if "slay" implies causing great admiration.

* εκπλήσσω (ekplḗssō): This means "to amaze," "to astonish," or "to surprise." This works if "slay" refers to shocking someone with how good something is.

To choose the best word, you need to specify what is being "slayed" and how.