from The American Heritage® Dictionary of the English Language, 4th Edition
- n. Biology A main axis or shaft, such as the main stem of an inflorescence, the stalk of a pinnately compound leaf, or the spinal column.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. The main shaft of either a compound leaf, head of grain, or fern frond.
- n. The spine or the vertebrae of the spine.
- n. The central shaft of a feather.
from the GNU version of the Collaborative International Dictionary of English
- n. The spine; the vertebral column.
- n. Same as Rhachis.
from The Century Dictionary and Cyclopedia
- n. In botany:
- n. The axis of an inflorescence when somewhat elongated; the continuation of the peduncle along which the flowers are ranged, as in a spike or a raceme.
- n. In a pinnately compound leaf or frond, the prolongation of the petiole along which the leaflets or pinnæ are disposed, corresponding to the midrib of a pinnately veined simple leaf. See cut under compound.
- n. In zoöl. and anatomy:
- n. The vertebral column.
- n. The stem, shaft, or scape of a feather, as distinguished from the web, vane, or vexillum; especially, that part of the stem which bears the vexillum. as distinguished from the calamus or quill. See quill, 4.
- n. The median part of the radula of a mollusk, usually bearing teeth which differ from those on each side of it.
- n. The axial skeleton of various polyp-colonies, as of Gorgonia; some axial part, or formation like a midrib, as in crinoids.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. axis of a compound leaf or compound inflorescence
- n. the series of vertebrae forming the axis of the skeleton and protecting the spinal cord
New Latin, from Greek rhakhis, spine, ridge.(American Heritage® Dictionary of the English Language, Fourth Edition)
From New Latin, from Ancient Greek ῥάχις ("spine, ridge"). (Wiktionary)