Over recent years, linguists have given an increasing amount of attention to impoliteness studies (Bousfield, 2008, Culpeper et al., 2003, Kienpointner, 1997, Meier, 1995a, Meier, 1995b and Mills, 2009). Oddly however, little attention has yet been paid to the semantics of the English word rude. Lacking precise translation equivalents in many languages, rude is a keyword revealing much about socially accepted ways of behaving in Anglo society (Wierzbicka, 1997; cf. Fox, 2004). In Australian English, as in English generally, it is the primary ethno-descriptor in the domain of "impoliteness". This paper provides a detailed lexical semantic analysis of rude in the productive formula It's rude to VP, and also in the fixed expression rude word. The semantic explications are framed in the simple universal primes of the Natural Semantic Metalanguage (NSM) (Goddard and Wierzbicka, 2002, Peeters, 2006 and Wierzbicka, 1996). The argumentation is supported by data on Australian English collected from Google searches.