ganglion

noun (plural ganglia /-glēə/ or ganglions)

• 1 Anatomy a structure containing a number of nerve cell bodies, typically linked by synapses, and often forming a swelling on a nerve fiber.
• a network of cells forming a nerve center in the nervous system of an invertebrate.
• a well-defined mass of gray matter within the central nervous system. See also basal ganglia.

• 2 Medicine an abnormal benign swelling on a tendon sheath.