Setete alla mattunud surnud jää pangaste sulamise või igikeltsa osalisest sulamisest tingitud maapinna vajumise tagajärjel tekkinud karstilehtrit meenutav sulglohk/negatiivne pinnavorm. Tavaliselt esinevad rühmiti suuremal alal meenutades kivimite lahustumisel kujunenud karstimaastikku, millest tuleneb ka termini 'karst' kasutamine, kuigi kivimite lahustumisega mingit seost pinnavormi kujunemisel ei ole (siit ka terminid 'ebakarst' ja 'pseudokarst'). Kohati esineb termokarsti lohkudes ajutisi järvi - termokarsti järved., (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.