The 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
A transientphysiologicalstate of suspension of obviousvital activities such as to enable an organism to escape the notice of its enemies or to conserve its energy. [http://www.merriam-webster.com/dictionary/parabiosis]
An alien form of life within an organism, commonly invasive, such as a growing cancer