1. An organism that kills part or all of another organism before deriving nutrients from it (usually applied to plant pathogens). 2. An organism that derives nutrients from dead plant or animal tissues, whether or not it is responsible for the death of those tissues. 
a microorganism feeding only on dead organic tissue.
An organism that causes the death of host tissues as it grows through them such that it is always colonising dead substrate.
A necrotroph is any parasitic organism that kills the living cells of its host and then feeds on the dead matter.
necrotroph An organism that feeds on dead tissues or cells.