The word "plicatoperipatus" is a scientific term that refers to a specific group of creatures within the family of Peripatidae, which are often known as velvet worms. These animals are not commonly discussed in everyday language, so you might not hear this word often outside of scientific contexts.
In summary, "plicatoperipatus" is a scientific name for a type of velvet worm. You would use it in specialized discussions about biology, and it does not have common synonyms or idiomatic expressions associated with it.