"Tin dog" is a term used to describe a robotic or metal dog-like creature. Synonyms for this term could include "metal mutt," "mechanical pooch," or "android canine." Other possible synonyms could be "cyber hound," "robo-pet," or "machine mongrel." These terms are all similar in that they evoke the idea of a dog-like creature made from artificial or mechanical materials, and are useful for descriptive purposes in science fiction stories or other contexts where robotic or artificial animals are involved.