rachis

‖n.; pl. E. Rhachises L. Rhachides [ See Rachis. ] [ Written also rechis. ] 1. (Anat.) The spine. [ 1913 Webster ]

2. (Bot.) (a) The continued stem or midrib of a pinnately compound leaf, as in a rose leaf or a fern. (b) The principal axis in a raceme, spike, panicle, or corymb. [ 1913 Webster ]

3. (Zool.) (a) The shaft of a feather. The rhachis of the after-shaft, or plumule, is called the hyporhachis. (b) The central cord in the stem of a crinoid. (c) The median part of the radula of a mollusk. (d) A central cord of the ovary of nematodes. [ 1913 Webster ]