Mima mound (Mi'-ma [my'-ma]). A term used in the NW U.S. for one of numerous low, circular or oval domes composed of loose, unstratified, gravelly silt and soil material, built upon glacial outwash on a hog-wallow landscape; the basal diameter varies from 3 m to >30 m, and the height from 30 cm to about 2 m. Named after the Mima Prairie in western Washington State. Cf: pimple mound.