"Dissipator" is not a very commonly used word and therefore has very few synonyms that are commonly known. However, the word "dissipate" means to scatter or disperse, and therefore words that can be used as synonyms for "dissipator" include "scattershot," "disperser," or "scatterbrained." In a more technical sense, "dissipator" can refer to a device that dissipates energy, in which case words like "heat sink" or "cooling system" could be used in place of "dissipator." In general, the context in which "dissipator" is used will determine which synonyms are most appropriate.