united at the xiphoid process.
the condition of being such a twin.
conjoined twins are identical twins. in both types of twins, the embryo is supposed to separate during the first two weeks after conception; however, in conjoined twins the embryo does not separate in two. the types of conjoined twins are based on the location of the fusion, and include thoracopagus or xiphopagus, omphalopagus, craniopagus, parapagus, pygopagus, ischiopagus, and rachipagus or rachiopagus. medicinenet.com