nerve? cord` n. 1. the hollow dorsal tract of nervous tissue that constitutes the central nervous system of all chordates and that developed as the spinal cord and brain of vertebrates. 2. a double strand of nerve fibers in elongate invertebrates, as earthworms, that connects with a pair of nerve ganglia at each body segment. [1875?80] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.