ChiÂ·nook. n. pl. Chinook or ChiÂ·nooks. 1. a. A member of a Native American people formerly inhabiting the lower Columbia River valley and adjoining coastal regions of Washington and Oregon, now located in western Washington.The Chinook traded widely throughout the Pacific Northwest.hinook. n pl-nook or-nooks. 1. (Peoples) a Native American people of the Pacific coast near the Columbia River. 2. (Languages) the language of this people, probably forming a separate branch of the Penutian phylum.