General terms:
* Saprotroph: This is the scientific term for an organism that gets its nutrients from dead organic matter.
* Decomposer: This is the most common term and is widely understood.
* Detritivore: This term is often used for animals that consume dead organic matter.
Specific terms:
* Fungi: A large group of decomposers.
* Bacteria: Another major group of decomposers.
* Scavenger: Often used for animals that consume carcasses.
* Rotter: A more informal term for something that decays.
The best alternative depends on the specific situation and the level of formality required.