noun
Usage: usually capitalized S
Etymology: so called after Chang died 1874 and Eng died 1874 congenitally united twins born in Meklong, Siam, of Chinese parentage
1.
a. : one of a pair of congenitally united twins in man or animals — compare craniopagus , thoracopagus , xiphopagus
b. : a double monster (as a conjoined fruit)
2. : one of two persons or things that are closely or indissolubly associated
distribution (the Siamese twin of production) — Lewis Galantiere