When someone is caught lying. How now is self explainitory. Brown Cow means that they are a liar. Works incredibly well if they are exposed for their lie.
Guy 1: Hey, I know what the capital of Illinois is. It's Chicago.
Guy 2: It's Springfield. How now brown cow?
Guy 2: It's Springfield. How now brown cow?
by gbee93 March 23, 2011
by Tepeki August 13, 2007