Definition of Glomerulus

Glomerulus: 1.In the kidney, a tiny ball-shaped structure composed of capillary blood vessels actively involved in the filtration of the blood to form urine. The glomerulus is one of the key structures that make up the nephron, the functional unit of the kidney.
2. In the olfactory bulb, an anatomically discrete module receiving input from an olfactory sensory neuron.

The glomerulus in the kidney was so named by the Italian anatomist Marcello Malpighi (1628-1694). The structure was once called a malphigian corpuscle. "Glomerulus" is the diminutive of the Latin "glomus" meaning "ball of yarn." It is literally a "little ball of yarn." Plural: glomeruli.