noun
: any of three crystalline oxalates of potassium:
a. : the normal efflorescent soluble salt K 2 C 2 O 4 .H 2 O used chiefly in preventing the clotting of blood (as in blood tests) and formerly in photography
b. : a bitter poisonous acid salt KHC 2 O 4 .H 2 O found especially in oxalis and rhubarb and used chiefly in removing ink stains and scouring metals; potassium hydrogen oxalate — called also potassium acid oxalate, salt of sorrel
c. : potassium tetroxalate