clot

American  

[klot] / klɒt /

noun

1. a mass or lump.

2. a semisolid mass, as of coagulated blood.

3. a small compact group of individuals.

   a clot of sightseers massed at the entrance.

4. British Informal. blockhead, dolt, clod.

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verb (used without object)

clotted, clotting

1. to form into clots; coagulate.

verb (used with object)

clotted, clotting

1. to cause to clot.

2. to cover with clots.

   Carefully aimed snowballs clotted the house.

3. to cause to become blocked or obscured.

   to clot the book's narrative with too many characters.

clot British  

/ klɒt /

noun

1. a soft thick lump or mass

   a clot of blood

2. informal a stupid person; fool

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verb

1. to form or cause to form into a soft thick lump or lumps

clot Scientific  

/ klŏt /

1. A soft insoluble mass formed when blood or lymph gels. During blood clotting, white blood cells, red blood cells, platelets, and various clotting factors interact in a cascade of chemical reactions initiated by a wound. When a body tissue is injured, calcium ions and platelets act on prothrombin to produce the enzyme thrombin. Thrombin then catalyzes the conversion of the protein fibrinogen into fibrin, a fibrous protein that holds the clot together. An abnormal clot inside the blood vessels or the heart (a thrombus or an embolus) can obstruct blood flow.

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Other Word Forms

• clottish adjective
• declot verb
• nonclotting adjective
• unclotted adjective

Etymology

Origin of clot

before 1000; Middle English; Old English clott lump; cognate with Middle Dutch klotte, German Klotz block, log ( klutz )

Explanation

A clot is a mass of coagulated blood. It's your body's way of repairing itself, stopping blood from flowing and beginning to heal a wound. You can use the noun clot for any liquid that forms a solid lump or mass, though it's usually a medical term specifically related to blood. Some clots are useful, like the ones that form on skin that's been cut, while others — like those that occur inside blood vessels — can be harmful. Clot can also be a verb, meaning to clog or coagulate. The root is the German word Klotz, which means "lump or block."

Example Sentences

A family say their mother was let down in the worst possible way when she died after being sent home from hospital with a blood clot on her lungs.

From BBC • Feb. 12, 2026

Emmy-winning actress Catherine O'Hara, who starred in "Schitt's Creek" and "Home Alone," died from a blood clot in her lungs, her death certificate revealed Monday.

From Barron's • Feb. 9, 2026

Another doctor discovered a significant blood clot running from the middle of her calf, all the way up near her belly.

From Los Angeles Times • Dec. 30, 2025

I was visiting my daughter’s family there, and my doctor back home texted me that my out-of-the-blue swollen ankle might mean a blood clot.

From The Wall Street Journal • Dec. 18, 2025

Others proposed that Garfield's chest pain shortly before death was more likely the result of a blood clot in his heart.

From "Ambushed!" by Gail Jarrow

Related Words

• clotting
• clump
• lump