Technically, it's not a wolf or any Terran animal at all. It's supposed to refer to the canine-like animals that accompanied the guards on Rura Penthe, which Memory Alpha calls "jackal mastiffs". If you were writing Klingon "in-character", you'd use tera' qovIj or tera' ngavyaw' to refer to Earth animals using Klingon analogues, but sometimes people drop the tera' if they're talking about day-to-day experiences with Earth animals. There's no chance for confusion, since ngavyaw'mey do not, strictly speaking, actually exist.

There's no official distinction yet for whether a given Earth canine would be a tera' qovIj or a tera' ngavyaw'. Many people who make a distinction seem to base their reasoning on the size of the Earth animal, and also the puns. (We know that a qovIj is smaller than a ngavyaw'. ngavyaw' is a pun based on a literary wolf dog, whereas qovIj is a pun based off a stereotypical pet dog name.) Using ngavyaw' for a wolf isn't exactly canon. It's probably closer to the unofficial but widespread use of jabbI'ID "data transmission" as a term for "email".