(not in technical use) conjoined twin.
Origin of Siamese twin
First recorded in 1820–30; named after congenitally united twins, Chang and Eng (1811–74), born in Siam, who were joined to each other at the chest
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for siamese twins
non-technical name for conjoined twins
Word Origin for Siamese twins
C19: named after a famous pair of conjoined twins, Chang and Eng (1811–74), who were born in Siam
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
Medicine definitions for siamese twins
[ sī′ə-mēz′ ]
Either of a pair of conjoined twins. No longer in technical use.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.