conjoined twin

noun
  1. either of a pair of identical twins born with their bodies joined together in some manner, having failed to separate completely in utero.
See also Siamese twin.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for conjoined twins

conjoined twins

pl n
  1. twin babies born joined together at some point, such as at the hips. Some have lived for many years without being surgically separatedNon-technical name: Siamese twins
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

conjoined twins in Medicine

conjoined twins

pl.n.
  1. Identical twins born with their bodies joined at some point and having varying degrees of residual duplication, a result of the incomplete division of the ovum from which the twins developed.diplosomia
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.