A clot is a word used to refer to a viscous, thick, coagulated mass of some substance, usually blood. It is also sometimes used to refer to a clump, mass, or lump of some material, such as clay, but this is a more uncommon use. Basically, a clot is a viscous mass of blood. The Chimera portion comes from the Chimera portion in Greek mythology (see Khimaira), but refers to the blood of entities called chimeras in FFXI, specifically Lamiae & Merrows. Thus, the Chimera Clot would be a sentient clot of the blood of a Lamia (or Merrow). However, clot-type monsters in Vana'diel are simply a subspecies of slimes, so the name is likely just an exaggeration or instance of creative naming.