parabiosis

noun5

1. •
   The (natural or surgical) union of parts of two organisms, especially in such a way as to cause them to share their vascular systems. Organisms so joined then are called parabionts.

   • Parabiosis is the condition of more than one living organism joined ..., with ... circulatory fluids being exchanged among the parabionts. — 2019
2. •
   The fusion of two embryos to form conjoined twins

   • Conjoined identical twins... could be thought of as parabionts. — 2019
3. •
   A transient physiological state of suspension of obvious vital activities such as to enable an organism to escape the notice of its enemies or to conserve its energy.
4. •
   A form of symbiosis, typically among ants, in which different species share common nest galleries but maintain distinct broods and do not practice mutualism other than incidentally.
5. •
   An alien form of life within an organism, commonly invasive, such as a growing cancer.

   • …the fever sperm coming into ... the living frame ... is able to create a sort of other life or parabiosis within it .... — 1873