[sef-uh-loh-thawr-aks, -thohr-]
noun, plural ceph·a·lo·tho·rax·es, ceph·a·lo·tho·ra·ces [sef-uh-loh-thawr-uh-seez, -thohr-] /ˌsɛf ə loʊˈθɔr əˌsiz, -ˈθoʊr-/. Zoology.
  1. the anterior part of the body in certain arachnids and crustaceans, consisting of the coalesced head and thorax.

Origin of cephalothorax

First recorded in 1825–35; cephalo- + thorax
Related formsceph·a·lo·tho·rac·ic [sef-uh-loh-thuh-ras-ik] /ˌsɛf ə loʊ θəˈræs ɪk/, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for cephalothoracic


noun plural -raxes or -races (-rəˌsiːz)
  1. the anterior part of many crustaceans and some other arthropods consisting of a united head and thorax
Derived Formscephalothoracic (ˌsɛfələʊθəˈræsɪk), adjective
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for cephalothoracic



1829, from cephalo- + thorax. Perhaps from French or German.

Online Etymology Dictionary, © 2010 Douglas Harper

cephalothoracic in Medicine


  1. Relating to the head and the chest.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

cephalothoracic in Science


  1. The combined head and thorax of arachnids, such as spiders, and of many crustaceans, such as crabs.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.