part of has part has quality composed primarily of watercourse depressed landform riverine pothole FTT:1071 A depression which 1) has smooth surfaces, 2) has a bowl-like or cylindrical shape, 3) results from the erosion of the rocky bed of a watercourse. churn hole eddy mill evorsion giant's kettle kettle kolk pot rock mill stream kettle swirlhole rock solid surface layer surface landform smooth cylindrical U-shaped tubular