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1.
A more derogatory version of half caste used to describe people of mixed race. Made more offensive maybe by the implied casually dismissive nature of the phrase. Often pronounced arf chat.

Regionally popular in the UK (South Eastern England among older people and possibly a phrase coined by soldiers during the British colonial occupation of India in the 19th century.
“Ooh… what a beautiful baby. Shame she looks a bit half chat though. Who's the father?”
by Chelonian October 06, 2011