The word "ruster" can be defined as someone who covers metal objects with rust. Synonyms for "ruster" can include "oxidizer", "corroder", "rust generator", or "rust inducer". These words describe the same action of rusting metal objects. Other related terms that can be used in place of "ruster" might include "rusting agent", "corrosive", or "oxidizing agent". Whether describing a person or chemical substance, these terms all reflect the same process of causing metal objects to rust and corrode. It is important to note that this process can have harmful effects on the longevity and durability of the metal material.