: a specialized cell, group of cells, or organ of endothelial origin that selectively removes materials from the blood, concentrates or alters them, and secretes them for further use in the body or for elimination from the body compare endocrine gland, exocrine gland
b
: any of various animal structures suggestive of glands though not secretory in function
2
: any of various secreting organs (such as a nectary) of plants