A natural bobtail is an animal's tail which due to a mutated gene grows unusually short or is missing completely. The genes for the shortened tail may be dominant or recessive.

What does bobtail mean in trucking?

A semi-truck is in “bobtail” mode when it does not have a trailer attached. Truck drivers often drive a bobtail truck when they are on their way to pick up their cargo at the beginning of a shift, or after dropping their cargo off at the end.

Why do truckers call it bobtail?

A bobtail truck is a truck without a trailer attached to it. The name is thought to have come from the Bobtail cat, a breed of cat with a distinctly stubby “bobbed” tail (not to be confused with the bobcat).