An organism which has to acquire its energy by digesting food that has been manufactured by other organisms. Thus all organisms are heterotrophes except the primary producers which can manufacture their own food, usually by photosynthesis. Heterotrophy is the process whereby existing organic molecules are used by an organism for its energy needs, in maintenance, growth, and reproduction. See Stear (2010) Limnol. Oceanogr. 5, 2, 817 on drivers of net heterotrophy in contrasting lakes.

http://bugs.bio.usyd.edu.au/learning/resources/Mycology/Feeding/heterotrophy.shtml Website on Fungal biology.