What term is used to describe a free floating matter in the blood or lymph that is moving?

The term that describes free-floating matter in the blood or lymph, which can travel through the circulatory system, is "embolus." An embolus can be composed of various materials, including a blood clot, air bubble, fat globule, or other substances that are carried by the bloodstream. When an embolus lodges in a blood vessel, it can lead to serious complications such as obstruction of blood flow, potentially causing tissue damage or necrosis depending on where it occurs.

In medical terms, it is important to differentiate an embolus from a thrombus; a thrombus is a blood clot that is attached to a vessel wall and has not detached. Clots generally refer to blood that has coagulated, and while they can include thrombi, they do not specify the free-floating aspect that identifies an embolus. Serum refers to the clear liquid that separates from blood when it clots and is not related to the concept of movable matter within the bloodstream or lymphatic system.