The phrase "curdled blood" refers to blood that has thickened and clotted due to exposure to air or coagulation. Synonyms for this phrase might include "congealed blood," "coagulated blood," "clotted blood," or "thickened blood." These phrases all convey a similar meaning, describing blood that has undergone a chemical change and become more viscous or solid. Alternatively, one might describe "curdled blood" as "solidified blood," "jellied blood," or "gelatinous blood." These more descriptive phrases may convey the sense of revulsion or horror that often accompanies references to curdled or clotted blood.