Question

Parasitism is the act of one organism feeding on and usually living on or in another, typically larger organism. The feeding organism is called a parasite. What is the term describing the organism that is being fed upon in parasitism?

Answer 1

In parasitism , the organism on which the parasite feeds upon is called host.

Explanation:

           Parasitism is the phenomenon in which one organism is dependent on another organism, partially or completely for its survival.
           The organism may be a total parasite if it is completely dependent upon another organism, including nutrition. Such plants are called total parasites. 
           The plant on which the parasite is dependent is called host.
           Many plants like Viscum are autotrophs, i.e. these can synthesize organic food during [photosynthesis](http://socratic.org/biology/energy-in-organisms/photosynthesis). 
           These plants contain chlorophyll. These are dependent upon host only for attachment and support. These draw water and mineral nutrients from the host. Such plants are called partial parasites. 
         The term "host" is applied in both cases, irrespective of whether the organism is completely or partially dependent on it.
         Animals are always total parasites. Examples of total and partial parasites occur in plant kingdom.