Hong Kong Code-mixing Dictionary

Definition: (vulgar, textspeak) A code-mixing term used by native Hong Kongers to describe someone who's idiotic and stupid. It originated from the Cantonese words '憨鳩' because the '鳩' (penis) has a similar pronunciation as the number 9 in Cantonese.

Usage: E.g. Why did you piss on me? Are you on9? (憨鳩) E.g. Don't be so on99 and watch where you're going! (憨鳩鳩)

Synonym: 憨鳩

Reference: https://languagelog.ldc.upenn.edu/nll/?p=28512