unevenness; bumpiness; roughness; imbalance; inequality; unevenness
unevenness; roughness; ruggedness; inequality; imbalance; unevenness
hollow; low ground; basin; pit; dip; depression
concavity; hollow; depression
concave angle; (a) re-entrant
concave polygon; non-convex polygon
indentation; recessus; vallecula; concavity