setete alla mattunud surnud jää pangaste sulamise või igikeltsa osalisest sulamisest tingitud maapinna vajumise tagajärjel tekkinud karstilehtrit meenutav sulglohk/negatiivne pinnavorm, (karst)sinkhole like hollow formed due to soil subsidence as buried dead ice block thaws or as ice-rich permafrost thaws: occurs in periglacial areas/conditions. Usually appear as hollow assemblage (landscape) resembling those formed by solution in some karst areas which is how they came to have karst attached to their name. The related term - thermokarst lake (thaw lake) refers to a body of freshwater, usually shallow, that is formed in a depression by meltwater from thawing permafrost, often temporary lakes called also permafrost thaw ponds.