To make something become nothing; to reject or cancel.
Nix the last order – the customer walked out.
1977-1980, Lou Sullivan, personal diary, quoted in 2019, Ellis Martin, Zach Ozma (editors), We Both Laughed In Pleasure
He said his roommate had reacted favorably & said he "wanted to share the bed" with him! So I figured that nixed me out of the picture at least for now.
To destroy or eradicate.
interjection
No! Not at all!
(obsolete) A warning cry when a policeman or schoolmaster etc. was seen approaching.