Real Dictionary

nix
transitive verb: If you nix a plan or suggestion, you reject or forbid it.

nix in American English 1
a water sprite, usually small and of human or partly human form
adverb: no
interjection: (used as an exclamation, esp. of warning)
noun: nothing
transitive verb: to veto; refuse to agree to; prohibit

nix in American English 2
no
nothing
stop; don't do that
to disapprove of or put a stop to
noun: a water spirit that draws its victims into its underwater home

nix in British English 1
noun: a rejection or refusal
sentence substitute
verb: to veto, deny, reject, or forbid (plans, suggestions, etc)

nix in British English 2
noun: a male water sprite, usually unfriendly to humans