An informal name for a heavy road locomotive, regardless of its power source. While originally referring to the rhythmic exhaust of steam engines working hard upgrade, crews still use the term for hard-pulling diesel-electric units dragging heavy freight.
Heard on the job
We had a pair of big chuggers on the head end and they still struggled to get that drag over the hill.
Insider tip
Rookies might think this only applies to old steam engines, but veteran hoggers still use it for any heavy road power working hard.