lymph node

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of the small bodies located along the vessels of the lymphatic system (in humans notably in the neck, armpits, and groin) that filter bacteria and foreign particles from lymph fluid. During infection, lymph nodes may become swollen with activated lymphocytes.

from The Century Dictionary.

• noun One of numerous roundish, somewhat resistant bodies found along the course of the lymphatic vessels and composed of a mass of round cells in a delicate fibrous network.

from the GNU version of the Collaborative International Dictionary of English.

• (Anat.) A lymphatic gland.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun anatomy, immunology Small oval bodies of the lymphatic system, distributed along the lymphatic vessels, that are clustered in the armpits, groin, neck, chest and abdomen. They act as filters, with an internal honeycomb of connective tissue filled with lymphocytes and macrophages that collect and destroy bacteria, viruses and foreign matter from lymph. When the body is fighting an infection, these lymphocytes multiply rapidly and produce a characteristic swelling of the lymph nodes.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun the source of lymph and lymphocytes