Green’s Dictionary of Slang

(S.Afr.) a general term of approval, fantastic, great.

1974		Eng. Usage in Southern Afr. V:1 6: Kwaai, [...] a general term of approval, retaining only the force of ‘kwaai’ not the meaning — denotes anything from ‘good’ to ‘beautiful’.. a kwaai movie. She’s a kwaii goose. Kwaai, man, thanks [DSAE].
1980		E. Patel They Came at Dawn 9: The music is kwaai but nobody wants to d-a-n-c-e [DSAE].
2005		A. Lovejoy Acid Alex 126: I finished the second beer. I was feeling seriously fucking kwaai. I told Martin he was a kwaai dude too.
2008		Mail and Guardian (Johannesburg) 18 Apr. 🌐 My chommies and I have beaten up a couple of kaffirs. You are young, that‘s what you do. In those days your dad told you that’s kwaai (cool).
2011		Mail & Guardian (Johannesburg) 28 Mar. 🌐 Don Laka’s ‘kwaai’ township breezes.