one of a tribe of north american indians now living in the state of washington, noted for the custom of flattening their skulls. chinooks also called flathead indians.-a warm westerly wind from the country of the chinooks, sometimes experienced on the slope of the rocky mountains, in montana and the adjacent territory.-a jargon of words from various languages (the largest proportion of which is from that of the chinooks) generally understood by all the indian tribes of the northwestern territories of the united states.