lehtri-, lohu- või liua-kujuline, kuni mitmekümne meetrise (harvem üle 100 m) läbimõõduga suletud negatiivne pinnavorm, bowl-shaped, funnel-shaped, or vertical-sided depressions in the ground caused by karst processes (chemical dissolution of rocks) or suffosion (erosion of non-cohesive fines out of soil) induced collapse of voids in the ground; may vary in size from 1 to several hundred m both in diameter and depth.