Middle English, from Old English clott; akin to Middle High German klōz lump, ball
— more at clout
Date:
before 12th century
1: a portion of a substance adhering together in a thick nondescript mass (as of clay or gum)2 a: a roundish viscous lump formed by coagulation of a portion of liquid or by meltingb: a coagulated mass produced by clotting of blood3British:blockhead4:cluster, group<a clot of spectators>